C4 (84-96)

C4 BOSE WOES: Repairing & Replacing 84-96 Bose Speakers & Amps

by Chris Petris

lead shot

If you own a C-4 equipped with Bose sound system, you will eventually need Bose amplifier repair or replacement. Every Bose sound system equipped C-4 uses one amplifier per speaker. This is the weak link. Amplifier capacitors are filled with electrolytic fluid which ultimately leaks out onto the circuit board causing failure. If the leak is slow, the amplifier’s circuit board can be damaged beyond repair. Electrolytic fluid is acidic and will corrode anything it touches.

It is common to have multiple amplifier failures at one time. In most situations, you suddenly lose sound from a particular speaker. There have also been situations where all amplifiers fail. If one or two speakers stop working, check the amplifiers. When the radio receiver fails all sound output will be lost.

There are some differences in the early and late C-4 receivers. Early models (1984-1989) have integrated radio control head and receivers, while later models (1990-1996) have a separate receiver. The radio receiver is located under the passenger side dash in 1990-1993 cars; it’s located behind the passenger seat in the rear compartment of 1994-1996 Corvettes. Some failed 1990-1996 receivers will result in a cessation of sound output. The 1990-1996 radio head is only for controlling the receiver and to play CD or cassettes. The sound bites go to the receiver for output to speakers.

There are simple tests that can be performed to check the integrity of the amplifiers. If all speakers go out at once, the Bose relay should be checked first. (The relay has also been known to cause a dead battery from time to time.) The amplifiers should be inspected for dark staining of the circuit board, any burnt wires, or an odor of burnt plastic.

A common problem with 1984-1989 cars is water in the speaker/amplifier enclosure located in the door. If the door drain is not working, the enclosure can be submerged, allowing water to seep inside. The enclosure is sealed, but if it has been opened and the gasket was damaged, even rain water may seep inside through a bad outside seal strip. Severe radio receiver water damage may also occur from a leaking rear hatch window in 1994-1996 Corvettes. In some cases, the receiver is submerged in the compartment.

Speakers can be tested with an AA 1.5 volt battery. The receiver output can be checked with a voltmeter for varying current output to make sure the amplifier is receiving a signal. If adjusting the radio control knobs on 1984-1989 cars produces static or noise, the radio has a problem, not the speakers or amps. In some cases, just touching the control knobs causes static.

Removing the speaker/amplifier enclosure is not too difficult, except on 1990-1996 models. The front speaker enclosure is under the sill cover and requires sill removal to access. The cover sticks to the sill so care must be taken during removal. Slowly lift one side of the cover so the bond can loosen from the sound deadener. Try to avoid getting the sound deadener material on your clothes or skin because it is difficult to remove. Once the speaker/amplifier enclosures are removed, the speakers and amplifiers can be tested for proper signals.

You can repair or replace the amplifiers one at a time. If you are repairing the original amplifiers, you may want to do them all to avoid further circuit board damage. There are options: repair, replace the amplifiers, or get rid of the system altogether. Changing the system is costly because all the components must be replaced and the wiring must be modified. Although the original Bose system may not be capable of extreme bass, once repaired it is a high quality system that can be very reliable.

Beware of NOS (New Old Stock) amplifiers that are being sold as correct replacements; they may have different part numbers. The amplifiers are matched units to the receiver and, in some instances, sold as correct matching units from another application, which can degrade sound output. The part numbers must be the same as what was removed for proper operation. Don’t forget that NOS amplifiers may be working now, but how long will it be before they have capacitor issues?


The Bose amplifier relay (CC # 244409) is located under the passenger side dash on 1984-1989 cars. Unfortunately, you can only feel the relay, but the wiring is visible from under the dash. Follow the wiring to the relay and then pull it downward to release it from its retainer. The relay has a four wire connector with an orange wire (12 volt battery power from the courtesy fuse), pink with black tracer (power out to amplifier when radio is on), pink wire (power only when radio on), and black wire (ground to chassis under right side kick panel). The black wire should have a low ohm reading (indicating a good ground at all times). The relay is working properly as long as the pink wire has 12 volts when the radio is turned on. If pink wire has 12 volts when the radio is off, the relay is sticking, which will cause a dead battery.


The Bose amplifier relay on 1990-1996 cars (CC # 594343) is located under the dash on the driver’s side, to the right of the steering column. The carpeted knee bolster and aluminum reinforcement plate below the steering column were removed for this photo. The 1990 cars have the same wire colors and test procedure as the 1984-1989 cars. The 1991-1996 cars have a wire color change at the amplifier relay. The amplifier power wire from the relay is an orange wire in position 4 on the relay connector. The orange wire should have 12 volts when the radio is on.


Removing the speaker enclosure is necessary to gain access to the amplifier. Disassemble the speaker enclosure with a ¼ inch socket. During reassembly, be sure to put the cotton sound deadening material back in place. Be careful to correctly reinstall the wire bundle right back where it came from to avoid piercing the wiring with a screw during assembly. In some cases, the enclosure has a channel that the wiring goes in to prevent wire damage.


Here is a typical Bose amplifier with circuit board damage. The circuit board has a soldered wire harness on early cars. Later cars have harness connectors so the harness can be removed from the circuit board.


This is an easy way to check for proper speaker operation. If the speaker cone moves and a pop is heard when the battery is touched, the speaker is working.


This is the setup required to check the amplifier for proper signal from the radio. Connect a voltmeter set on low AC voltage to terminals C and D. With the radio on high, the voltage should vary between 0 and 1 volt. Check the pink or orange wire at the amplifier (depending on the year of the car) and test for 12 volts when the radio is on. The black ground wire should be checked for low ohms also.


If you remove your amplifier and the metal covers to find this mess, replacement is most likely required. Door speaker amplifier item number 524024 is for 1984-1985 Corvettes, 524062 for 1990-1996 convertibles, 524065 for 1990-1996 coupes. The 1990-1996 rear speaker (left side) part number for convertibles is 524046 for and 524043 for 1990-1996 coupes. Use the same part numbers for 1984-1989 convertibles and coupes.

C5 (97-04)

C5 Oil Pressure Sending Unit Replacement

by Chris Petris

If you haven’t already replaced the oil pressure sending unit (CC part # 305254) on your C5 Corvette, it will become a necessity when the gauge stops functioning properly. One telltale sign is the oil pressure gauge needle leaning past the high mark at all times or not moving from the lowest point. Another sign is an oil leak near the rear of the oil pan. Many times, the presence of oil is mistaken for a leaking rear main seal; always look at the top of the bellhousing for the source of a leak. If there is a trail of fresh oil cascading over the bellhousing, chances are the sending unit is leaking. Sending units have an immediately noticeable leak, whereas rear main seals usually experience a slow leak that increases over time.


This job will require you to remove your air cleaner, intake, and fuel rail, so if you have been considering an upgrade to any of these items now is the time.

You may or may not remove the fuel rail for this job, but if you decide to remove it before you tear into the engine, make sure to first remove the fuel pump fuse. Attempt to start the engine until all of the fuel is drawn out of the system. At first, the engine will start then die during cranking. Try this a few times until the engine does not start at all. This will decrease the amount of fuel in the rail. Then disconnect the battery.

When disconnecting the weather-pack connectors for the engine wire harness, be aware of the silicone seal used to prevent water, dirt, and debris from corroding the sensor connections. Many times, the seals fall off and are missed during reassembly, leaving a connection vulnerable to corrosion. Unfortunately, the seals are not available separately; they are considered part of the connector. In the shop, we always salvage the seals when we replace broken connectors, so it is feasible that a local repair shop may have a seal if need be.

01- Disconnect the mass air flow sensor connector from the air intake.

02- Disconnect the intake air temperature sensor from the air duct assembly.


03- Disconnect the throttle actuator connector.


04- Loosen the clamp that secures the intake bellows to the throttle body.


05- Disconnect the throttle position sensor.


05a- Disconnect the MAP and knock sensor connectors at the rear of the engine.


06- Disconnect the coil pack connectors on both rails. The fuel injector harness connectors and gray plastic wire supports are also removed. The gray plastic wire supports use a winged post to hold them in the fuel rail and a pair of needle nose pliers works well to collapse the wings on the post to release them.


07- Disconnect the PCV valve supply hose at the intake manifold.


08- Remove the (4) 10mm bolts and one 8mm bolt that secure the fuel rails. The 8mm bolt is an intake manifold retaining bolt that is used to ground the fuel rail to the engine via the stainless steel strap.


09- At this point, it is a good idea to use compressed air to remove any debris from the top of the engine prior to removing the fuel rails and intake manifold.


10- PB’laster or an equivalent lubricant (WD40-CRC) is sprayed into the bowls where the fuel injectors are inserted into the intake manifold, to help loosen the seals during removal. Rotate the injectors back and forth to let the lube work its way between the seal and intake.


11- Disconnect all injector connectors. Push the metal fastener wire inward while pulling up on the connector. The weather-pack seal is placed back inside the injector connector and pushed back into position with bent needle nose pliers.


12- Carefully remove the fuel rail and disconnect the fuel line. Lay it to the side, out of the way, until the task is completed.


13- Remove the (10) 8mm intake manifold bolts. The rear two bolts on the intake will not come out of the intake after loosening them. Make sure they are unthreaded fully and be sure to pull them upward, away from the cylinder heads, as the intake manifold is lifted off the engine.


14- Disconnect the brake booster vacuum hose from the booster as opposed to rear of the intake. It may be easier to remove the intake manifold with the hose still attached to the intake manifold, rather than trying to remove it from the rear of the engine. With the brake booster hose disconnected, remove the intake manifold and hose.


15- As you can see, the top side of this engine could use some TLC. Carefully insert clean rags into each port and use a vacuum to clean up the large debris. Next, use mineral spirits to remove any remaining debris.


16- Here is the culprit situated close to the firewall.


17- Use a deep 1-1/16” socket to remove the oil pressure sensor and replace it with a new sensor. This sensor is not the typical tapered pipe thread that was used for all the other GM engines past. A metric straight thread is used with an aluminum sealing ring for proper sensor sealing to the engine. 110 inch pounds of torque is all that is required for proper sealing.


18- Be sure to replace all intake manifold gaskets prior to reinstalling the manifold. Use the aid of a pick to remove them from their machined retaining groove. Remove all residual oil in the sealing grooves with brake cleaner or mineral spirits before installing the new seals.


19- The foam seal is used to limit the amount of debris that builds up under the intake manifold; most intake manifold gasket sets include them as part of the kit.


20- When it comes time to install the manifold, the most aggravating part is dealing with the plastic vacuum line that connects to the rear of the intake manifold. If GM had made the tube 4-6 inches longer, the task would be much easier. I make this tube assembly from 5/32 vacuum hose, two hard plastic vacuum connectors, and two soft rubber vacuum connectors to lengthen the tube assembly, for a much easier intake manifold installation. The straight end connects to the existing vacuum tube and the 90 degree end connects to the intake manifold.

Body & Paint

84-96 Door Outside Seal Strip Replacement

84-96 Door Outside Seal Strip Replacement

By Chris Petris

Automotive door sealing technology has improved dramatically from the early days when rain water came in from all angles. By 1969 GM changed the outer seal strip that wipes the glass clear on those damp mornings to do a good job of keeping water out of the door. In turn it kept water off of the door internals and off the backside of the fiber door panels. By 1984 the door outside seal strip was an integral part of door glass sealing. The downside was they were the most exposed seal strips to date subjecting them to the effects of UV deterioration much quicker than previous year Corvettes. You can help keep them around longer with an application of rubber protectant to replace the rubber solvent compounds removed after each wash job. Products like Adams V.R.T. Vinyl Rubber and Tire Dressing from Corvette Central P/N 106824 will keep your outside seal strips looking good for many years. This dressing brings back that new look without that greasy oily slick look, you can also touch it without fear of it coming off on your hands or clothes.

C4 Outside Seal Strip Replacement Lead Shot (1) (Medium)

Ultimately no matter how well you maintain your 1984-1996 Corvette; the doors will end up with a rough looking outside seal strip on the top edge of the door. From an aesthetic standpoint the tattered upper edge looks pretty bad no matter how good your paint or wax job is. The rubber compound dries up and large sections of the ¾ inch wide outside seal strip break off making them look ragged. While looks may not be so important requiring an immediate fix; the dried out material that is missing allows dirt and grit to enter the area below the seal strip. The dirt and grit collects in the two auxiliary strips mounted onto the outside seal strip that quells any door glass rattling that might occur. The grit eats at your window after a while and you end up with noticeable scratches. Those noticeable scratches are almost impossible to remove without replacing the side window glass.

C4 Outside Seal Strip Replacement Lead Shot (2) (Medium)

Another factor is water that passes into the door area on top of the window regulator and motor. While the seal strips do not completely eliminate water from entering the door on the outside upper edge it does limit water intrusion substantially. New seal strips will also eliminate annoying door glass rattles on rough roads or when closing the doors. While it is not the easiest task to accomplish, it is possible for the Saturday afternoon Do-It-Yourselfer to finish in one afternoon. Simple tools are required along with a drill, rivet tool and some patience. Corvette Central has a very nice pair of reproduction outside seal strips, part number 284067, at a very reasonable price making a definitive aesthetic improvement on your C4s exterior. The strips are correct in appearance and more importantly the retainers are in the right place for the easiest possible installation.

Let’s move on to the photo illustration installation of the strips. The task begins with door panel removal which varies from the 1984 to 1996 model years.

C4 Outside Seal Strip Replacement (01) (Medium)

Before you begin removing door panels on the 1984-1989 Corvette it is advisable to remove the courtesy fuse or remove the negative battery cable. The CTSY fuse will disable the door courtesy lights and save your illuminated entry module. If the courtesy lights are left on for extended periods of time (longer than fifteen to twenty minutes) the delay module overheats and burns up. 1990-1996 Corvettes do not have a standalone illuminated entry module they use the Central Control Module for courtesy light control. Leaving the courtesy lights on will not damage the CCM, they will auto shut-off if enough light is present or they have been on a predetermined amount of time. You also need to be aware that the door lock switches will still have power to them when the courtesy light fuse is removed. Your call, I suggest removing the negative battery cable.

C4 Outside Seal Strip Replacement (02) (Medium)

All C4 manual door lock knobs are a clip-on fit on the manual lock rod. This hooked small diameter pick works best pulling the knob off the rod.

C4 Outside Seal Strip Replacement (03) (Medium)

Here a plastic windshield tool is used to pop out the courtesy light lens assembly. There are two clips on the top side that hold the light assembly in place.

C4 Outside Seal Strip Replacement (04) (Medium)

The light assembly can be left hanging until all the screws are out and the bezel can be removed.

C4 Outside Seal Strip Replacement (05) (Medium)

There is a Phillips head screw in the door handle bezel under the courtesy light to remove in the 1990-1996 Corvettes.

C4 Outside Seal Strip Replacement (06) (Medium)

1990 and up door panels should have a Phillips head screw under the manual lock rod knob. I have found many 1994-1996 Corvettes that do not have this screw from what appears to be a factory door panel installation. Always check the area for a screw before attempting to remove the door panel bezel.

C4 Outside Seal Strip Replacement (07) (Medium)

All 1984-1996 C4 door panels have a screw centered in the door open handle bezel at the front that must be removed.

C4 Outside Seal Strip Replacement (08) (Medium)

The manual door lock rod must be pushed rearward to remove the door handle bezel. Remember that the door is locked, if you put the window up and leave the keys in the ignition during your window/door project. You know how I figured that out.

C4 Outside Seal Strip Replacement (09) (Medium)

The 1990-1996 door handle bezel fits snugly in the door panel usually you can remove it with your fingers at the top first. Remember the manual door lock rod has to be pushed upward and out of the bezel as the bottom section is pulled away from the door panel.

C4 Outside Seal Strip Replacement (10) (Medium)

Once the door panel bezel is removed the courtesy light connector can be uncoupled. These connectors are simple to uncouple by pushing the tab upward and pulling them apart.

C4 Outside Seal Strip Replacement (11) (Medium)

I use this plastic weatherstrip tool to remove the door lock switch connector especially if the battery is not disconnected. Check the wires at the switch connector they are often frayed especially early C4s. The wires are sometimes holding by just a few strands of wire. If the wires are breaking or ready to, Corvette Central has the side specific repair harness available part number 664496L for the left and 664496R for the right. These repair harnesses are for 1986-1996 Corvettes when GM used reverse polarity switches and five wires. 1984-1985 Corvettes use three wire connectors their part number is 664501R and 664501L.

C4 Outside Seal Strip Replacement (12) (Medium)

I leave the 1984-1989 door handle bezel in place because they are fragile and can crack easily if they are pulled out of the panel. The only screw to remove is the center screw under the front of the door release handle. Don’t forget to push back the manual lock rod to the locked position like the 90-96. The manual lock rod is then pushed upward and out as the panel is removed. Another concern is the courtesy light connector that must be disconnected before panel removal, it is easy to yank the door panel off the door and find out you just exploded the courtesy light switch. If that happens to occur Corvette Central has a repair harness with switch part number 664492. Once the 1984-1989 door panel is removed as an assembly the door lock switch connector can be accessed and removed like the 1990-1996.

C4 Outside Seal Strip Replacement (13) (Medium)

All C4 door panels have two screws in the armrest pull area that must be removed. Corvette Central has metal reinforcements to aid the OE plastic inserts for the 1984-1989 armrest pull area. The arm rest filler savers are part number 484497 and they will keep your door panel armrest in good shape for many years once installed. The 1990-1996 door panels has an integral arm rest pull that is part of the switch assembly.

C4 Outside Seal Strip Replacement (14) (Medium)

The 1990-1996 driver side armrest door pull/switch assembly has a clip at the top that slides under the door panel. Once the door armrest pull is removed pick up the armrest pull/switch assembly and let the front go downward as you pull backward. To throw a curve ball the 1990-1996 passenger side door panel has a screw under the window switch. The passenger side window switch pops into place and is easily removed with the plastic windshield tool. Once the switch is out look in the hole and you will find a 7mm screw holding a metal tab onto the door frame.

C4 Outside Seal Strip Replacement (15) (Medium)

A small plastic tab has to be moved away from the mirror position switch then the connector removed.

C4 Outside Seal Strip Replacement (16) (Medium)

The power window switch has two tabs to move outward then the connector can be pulled off. Take it easy with this connector; work it back and forth easing it out to prevent switch damage.

C4 Outside Seal Strip Replacement (17) (Medium)

1990-1993 Door panels will have a long screw in this position to remove.

C4 Outside Seal Strip Replacement (18) (Medium)

1984-1989 Bose Stereo equipped Corvettes will require speaker grille removal.

C4 Outside Seal Strip Replacement (19) (Medium)

1984-1993 Corvettes will have a row of screws at the bottom, these screws are often rusty might be a good idea to have a fresh set of Corvette Central P/N 344142 handy.

C4 Outside Seal Strip Replacement (20) (Medium)

There is a right and wrong way to remove the 1994-1996 lower door panel retainers. This interior trim tool works very well for removal of the plastic push-in fasteners. Unfortunately placing the metal tool on the plastic panel can scratch the door panel plastic surface.

C4 Outside Seal Strip Replacement (21) (Medium)

I prefer to place the tool under the door panel to pry the retainers out avoiding any plastic scratches. The tool is inserted until the inner V is seated against the plastic retainer and the handle is pulled outward releasing the retainer.

C4 Outside Seal Strip Replacement (22) (Medium)

All C4 doors have this screw at the rear of the door near the rear hatch release switch.

C4 Outside Seal Strip Replacement (23) (Medium)

The door panel is pulled upward off of the top side of the door frame. Make sure the wires and connectors are not caught as you remove the panel away from the door. You have one more connector to disconnect before taking the panel completely off. Remember the 1984-1989 door panel will have the courtesy light and door lock switch connections to disconnect before the panel is too far away from the door.

C4 Outside Seal Strip Replacement (24) (Medium)

All C4s will require the removal of the rear hatch or convertible tonneau cover switch harness connector. The tab is move upward and the connector pulled apart. Now the door panel can be pulled completely off the door.

C4 Outside Seal Strip Replacement (25) (Medium)

The rear upper weatherstrip 7mm hex head retaining screw is removed.

C4 Outside Seal Strip Replacement (26) (Medium)

The rear outer weatherstrip 7mm hex head screw is removed next.

C4 Outside Seal Strip Replacement (27) (Medium)

You need to pull the weatherstrip back enough to access the rivets, try to avoid rough handling of the fragile weatherstrip, especially if it is original. A wide blade scraper with a sharpened edge works well cutting the weatherstrip off the door. GM applied adhesive to the weatherstrip so it takes some effort to get it loose.

C4 Outside Seal Strip Replacement (28) (Medium)

The front upper portion of the weatherstrip must also be removed. There are two 7mm screws holding the weatherstrip at the outer edges.

C4 Outside Seal Strip Replacement (29) (Medium)

Like the rear of the door the weatherstrip is carefully pulled off the door.

C4 Outside Seal Strip Replacement (30) (Medium)

Finally at the door outer seal strip rivets for removal. There are three rivets that must be drilled out with a 3/16-inch drill bit. One rivet is placed at the front and rear of the seal strip along with one close to the backside of the mirror. The piece of rubber vacuum tubing is an inexpensive drill stop to avoid going into or through the outer door skin. That outer door skin can be closer than you think.

C4 Outside Seal Strip Replacement (31) (Medium)

This is an official drill stop and they are available at most hardware stores. The stop is held in place with a set screw and can be set at any depth.

C4 Outside Seal Strip Replacement (32) (Medium)

The next step is to loosen the door glass anti-rattle bumper at the front with a 10mm hex head socket. Try to avoid turning the screw out too much, losing the bumper, it can be found if the screw is removed completely, it will require some extra work fishing for it inside the door with a magnet.

C4 Outside Seal Strip Replacement (33) (Medium)

The rear door glass anti-rattle bumper is also loosened so the door glass can be pulled as close as possible to the inner side of the door frame. Be aware that tinting film applied to door glass can be damaged when the door glass

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anti-rattle bumpers are loose. The window regulator upper mount has some sharp edges that will dig into the tint film. If you have tint you may want to put some duct tape on the top side of the regulator mount area. The window regulator mounts in the center of the door with two 10mm screws.

C4 Outside Seal Strip Replacement (34) (Medium)

Once the rivets are removed the seal strip should be pulled towards the inside of the door from front to rear. The idea is to release the retaining clips by pulling the strip towards you, once the clips are loosened up the strip is pulled upward.

C4 Outside Seal Strip Replacement (35) (Medium)

The seal strip sometimes requires a bit of a wrestling match to coax it out of the clips. The seal strip comes out easier as one single back and upward motion, as opposed to trying to get one end up, it binds the other clips if you go that direction. To avoid paint damage placing a screwdriver on the outside edge of the door and prying upward is not recommended.

C4 Outside Seal Strip Replacement (36) (Medium)

This gives you an idea of the objective each metal retainer clip must go into the oval slot in the door frame. Do not try to push the seal strip down into the oval slots until all the retaining clips are started into each oval slot. The new strips are a thing of beauty once installed properly, trying to push some of the retainers in while other are not in place will distort the metal substrate. Once the seal strip is distorted it is very difficult to make it look correct.

C4 Outside Seal Strip Replacement (37) (Medium)

With the seal strip in place it is time to make sure the outer lip goes over the door edge properly. At the back end it is easy to use this plastic windshield installation tool to coax the rubber on top of the edge before the rivet is installed. Many times the same thing happens at the front end of the seal strip between the mirror and the front edge of the door, I have found that I need to pick up slightly on the seal strip before trying to get the install tool under the rubber strip. The idea is to pick it up enough to allow correct placement of the strip without pulling it out of the retainers. Forcing the tool into the rubber can cut it, using a screwdriver can hurt the paint.

C4 Outside Seal Strip Replacement (38) (Medium)

Now the supplied 3/16-inch rivets are installed at the front, center and rear. Sometimes I may need to run a 3/16 inch drill bit (with the depth stop installed) into the seal strip and door frame rivet-hole if the rivet does not want to go in easily.

C4 Outside Seal Strip Replacement (39) (Medium)

It is easy to loosen the anti-rattle bumpers too far and they drop into the door as I did this time. It takes a bit of dexterity to place the anti-rattle bumper into place for the 10mm hex head screw installation. You can see where the exterior paint was removed from the 10mm hex head screw we call this the witness marks. Try to place the screw back in the same position or witness mark.

C4 Outside Seal Strip Replacement (40) (Medium)

The front anti-rattle bumper usually requires a finger or two in between the door frame pushing the glass away from the inside of the door, while the bumper is also pushed back into the same position it was. Same as the rear anti-rattle bumper stop place the screw in the “witness marks”.

C4 Outside Seal Strip Replacement (41) (Medium)

Once the rivets and anti-rattle bumpers are back in place the weatherstrips are glued back on the front and rear upper corners. You will be able to see where the factory placed the adhesive, follow those guidelines.

C4 Outside Seal Strip Replacement (42) (Medium)

This is the typical 1990-1996 under door panel foam weather shield. Corvette Central has the correct fitting insulator/barrier panels to replace the often torn originals. The replacement insulator/barriers can be fitted to the 1984-1996 (some cars used a thin plastic barrier) Use part number 284084L for the left side and 284084R for the right side on all C4s. The installation of the foam barriers will help quieten the interior.









C1 (53-62)

The Other Way Of Stopping Wilwood C1 Front Disc Brakes

The Other Way Of Stopping Wilwood C1 Front Disc Brakes

By Jay Heath


Wilwood front disc brakes help turn our fishtailing ’58 into a decelerating dynamo

As recent auction results make clear, ’53-’62 Corvettes continue to rank among the most desirable U.S.-built vehicles in the collector-car marketplace. Credit the car’s historical significance and timeless good looks, traits blissfully undiminished by the inexorable forward marches of time and automotive technology.

If only the same could be said of the C1’s driving dynamics, which not surprisingly mirror those of the ’49 Chevy Special/Deluxe with which the car shares the bulk of its mechanicals. Factor in the cost of OEM replacement parts and a driving position seemingly optimized for 13-year-old Romanian gymnasts, and it’s easy to see why many of these classic roadsters were long ago consigned exclusively to show or parade duty.

Fortunately for that subset of C1 owners who want to use their cars as, well, cars, the aftermarket brims with products designed to bring the early Vette’s driveability and functionality into concinnity with its iconic styling. When it comes to braking, perhaps the single most transformative upgrade one can make to a first-gen is to install a modern disc setup in place of the old-tech drums, a swap that vastly improves not only performance, but safety, ease of maintenance, and driver confidence as well.

In the case of our Signet Red ’58 project, an unswerving focus on functional, affordable modifications meant locating high-performance discs that were compatible with the factory frame and suspension hardware (what was left of it, anyway). You’ll recall that we paved the way for just such a conversion when we bolted up a quartet of 15-inch American Racing Torq-Thrust II wheels from Corvette Central a few months back (“Starring Roll,” Nov. ’13). The rims’ five-spoke design and generous internal clearance made them ideal for not only housing a modern set of binders, but showing them off as well.


The front half of our brake upgrade comprised a pair Forged Dynalite Pro rotors, along with four-piston calipers. (We’ll install the master cylinder in Part 2.) Note that Wilwood’s kits come complete with pads, hoses, and a full complement of installation hardware.

When it came time to select our kit, we turned to the experts at

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Wilwood for guidance. Established in 1977, the Camarillo, California– based company has established itself as one of the aftermarket’s premier manufacturers of high-performance brake components for a wide variety of vehicles, including every generation of Corvette.

Taking into account that our ’58 is a bit of a mongrel—those aftermarket wheels and a previously installed 9-inch rearend being the chief deviations from factory form—Wilwood’s Dustin Burr assembled for us a custom setup comprising 11-inch drilled-and-slotted rotors and four-piston calipers for each corner, along with a master cylinder and proportioning valve. (Note that because every car represents something of a unique case, Wilwood strongly recommends that customers contact the company for a specific recommendation before placing an order.)

Sadly, certain factors prevented us from performing baseline brake testing with the stock hardware, not the least of which was the car’s unnerving tendency to immediately lock up one or more wheels and initiate a lurid, tire-smoking slide at the slightest hint of pedal pressure. So unpredictable was the car’s braking performance, in fact, that even normally unflappable test pilot/coconspirator Greg Lovell was loath to complete the planned test session. Following the old maxim about discretion being the better part of valor—especially when dealing with someone else’s classic Corvette—we elected to forgo the panic stops and skip ahead to the install.

We’ll be splitting the front- and rear-brake installations into two separate installments, the better to highlight the unique aspects of each. Let’s take a look at the anterior end now, as we start to get our slip-sliding C1 on the road back to stopping salubrity.


AntiVenom’s Greg Lovell begins the job by securing the car on jackstands and removing the front wheels.


With the rims out of the way, we can observe the finest in midcentury braking technology up close. Yes, people really did race on these back in the day.


Popping off the dust cap with a screwdriver provides access to the nut that secures the hub.


Remove the nut, and you should be able slide the hub right off.


Note that the factory hub is equipped with ball bearings. As we’ll see shortly, the Wilwood kit features roller bearings for improved performance and durability.


All that remains of the stock braking hardware at this point is the backing plate. Note that in an apparent concession to modernity (and convenience), a previous owner added a self-adjusting spring mechanism at some point.

To liberate the plate assembly, you’ll need to secure the nut on the interior surface with an open-ended wrench while removing the four bolts on the front.

1958-chevrolet-corvette-spindle-10 1958-chevrolet-corvette-brake-hose-11

With the backing plate gone, we can get a good luck at the grime-caked factory spindle. Note that the brake hose can also be disconnected at this point, allowing the old fluid to drain into a pan below.

1958-chevrolet-corvette-clean-spindle-simple-green-12 1958-chevrolet-corvette-clean-spindle-lacquer-thinner-13

This seemed like a good time to do a little underside detailing, so Lovell hit the area with a little Simple Green and a wire brush. More-drastic measures were ultimately deemed necessary, however, at which point a few shots of brake cleaner and lacquer thinner (shown) took care of the most obdurate crud.

1958-chevrolet-corvette-towel-spindle-14 1958-chevrolet-corvette-clean-spindle-15

Following a quick-mop-up with a shop towel, the spindle emerges in all its Eisenhower-era glory.


It’s time to move over the workbench and start putting together the first hub-and-rotor assembly. Fortunately Wilwood provides step-by-step directions to walk you through the process.


Lovell begins by applying Lucas “Red ‘n’ Tacky #2″ grease to the inner (shown) and outer wheel bearings. As we noted earlier, the Wilwood bearings use a modern roller configuration.


The bearings then go into the hub, as shown here. Note that in this photo, the seal has not yet been installed.


After tapping in the seal with a rubber mallet, Lovell applies blue Loctite to the hub studs before torquing them down.


The next step is to bolt the hub to the rotor adapter, again using Loctite on the threads.


Before affixing the rotor to the adapter (using more Loctite, natch), we snapped this photo of its internal vanes. The vanes greatly improve cooling as compared with the old solid-rotor configurations.


Here’s the completed hub-and-rotor assembly, ready to bolt up to the car.


Since the original spindle wasn’t designed to accommodate disc brakes, Wilwood helpfully includes this caliper-mounting bracket. You’ll need to bolt it into place (yep, more Loctite) before installing the new brakes.


It’s time to bolt on the hub and rotor, applying some extra grease to the spindle-nut area along the way.


While you can reuse your old spindle nut, you will need to install the new, thicker washer (right) that comes with the Wilwood kit.


Here’s the finished assembly, complete with nut and washer. Give yourself bonus points if something looks a little “off” in this photo.


That’s right: We installed the left-side rotor on the right side of the car—this, despite the fact that Wilwood includes directional indicators on each one. Always remember to check your work as you go!


After straightening out our rotor snafu, it was time to bolt on the new natty, Wilwood four-piston calipers. They come with matching high- performance pads, one of which Lovell is shown installing here.


The caliper then bolts to the previously installed adapter…


…and the first half of our front-brake upgrade is complete. Note that the protective black coating on the rotors will wear off with use, revealing a gleaming silver finish beneath.


With the wheel reinstalled, the transformative nature of our brake upgrade starts to become apparent.


Our kit offered a choice of black-anodized or red-powdercoated calipers. We chose the latter, both to match the Signet Red finish of the car and to draw attention to the upgrade itself. Snazzy, no?


This article was originally published on http://www.superchevy.com/how-to/brakes/1407-the-other-way-of-stopping-part-1-wilwood-front-disc-brakes/viewall.html














C5 (97-04)

1997-2013 Rear Anti-roll / Sway Bar Link Replacement

1997-2013 Rear Anti-roll / Sway Bar Link Replacement

By Chris Petris

When we had a chance to look under the first C5 in 1997 it was hard to believe a performance vehicle would have a plastic anti-roll (sway bar) link. To make things difficult lock nuts were used to hold the links stud into the control arms. That meant when someone removed the end link chances are they would rip the joints seal because they did not hold onto the stud during removal. The original plastic sway bar end links flexed under hard cornering making the anti-roll bar less beneficial. Of course a hard driving Corvette owner might break one or more on a track day. By 2002 GM finally dropped the plastic pieces replacing them with an aluminum anti-roll bar end link. One of the few things that did occur positive is the same end link is used from 1997-2013 so you can easily find and replace the weak original 1997-2001 links. If someone was not being careful and tore the end link seal during suspension service you may need to replace one or more on your 2002-2013 Corvette.

Corvette Central has the anti-roll bar end link you need in stock form or heavy-duty performance Heim joint style end links. The installation is simple and does not require much time or many tools to complete. We often replace the end links when replacing shocks making a simple job even easier. The most important thing to remember when replacing the end links; the wheels should be hanging free on the front or rear. If one wheel is hanging free and the other wheel is loaded the end link will also be loaded making it difficult to remove and possibly dangerous. This is not something you can do by jacking up one side of the Corvette at a time; it must be done with the front or rear jacked up. The following photos will show you how it’s done.

Anti-roll Bar Link Replacement 01 (Medium)

An 18mm wrench is used to turn the nut while a T40 Torx bit holds the stud. Of course you can spin the stud on the

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old pieces for removal.

Anti-roll Bar Link Replacement 02 (Medium)

You can see the difference in this original 1999 anti-roll bar end link which has some distortion from age. The aluminum end links available from Corvette Central are stout pieces with new rubber seals.

Anti-roll Bar Link Replacement 03 (Medium)

The new end links are installed in the same manner as removal except an 8mm wrench is used to hold the stud. The 8mm hex on the end of the stud makes the job easier during the tightening process.

Anti-roll Bar Link Replacement 04 (Medium)

Once the nut is tightened on the stud with your 18mm wrench a torque wrench can be used to finish the job. All of the anti-roll bar end link stud nuts are torqued to 53 foot pounds or 72 Newton meters.



C5 (97-04)

1997-2013 Shock Absorber Information and Replacement

1997-2013 Shock Absorber Replacement

By Chris Petris

Shock absorbers are considered a consumable product with a limited lifespan here’s why…

Shock-mono-tubeThe C5 Corvette shock absorbers and C6 Corvette shock absorbers are both Mono-tube design. Mono-tube shock absorbers construction begins with a single cylinder (tube) filled with hydraulic fluid. Another piston is used to separate the gas charge from the oil charge. Together the hydraulic oil and high pressure gas with proper valving dampen suspension oscillations. The rod that protrudes out of the cylinder is connected to a piston with seals to keep fluid in check. Another seal is used at the end of the cylinder where the connecting rod comes out to keep the fluid and gasses in while trying to keep debris out. One of the major benefits of mono-tube shocks is the pressurized gas is separated from the oil via a piston. The constant gas pressure on the hydraulic oil minimizes aeration of the hydraulic oil preventing foaming. Foam affects shock absorber performance because it can be compressed while fluid cannot, in turn; the shock reacts quicker with predictability. Overall suspension performance is enhanced with quicker reaction times with the tire on the pavement as much as possible.

Now we delve into the controversial subject of when shock absorbers should be replaced.

The shock absorber piston seal wears from rapid movement depending on how rough the road surfaces you traverse. Also dependent on the environment the shocks rod end seal wears from grit, dust or just plain dirt that coats the shocks rod surface. A light film of oil is present on the exterior of the shock absorbers exposed connecting rod attracting debris which is unavoidable. You can expect to see evidence of slight seepage on the shock absorbers cylinders exterior over a long period of time. It appears as a stain not wet to the touch, if there is a film of oil present on the exterior of the shock absorber, emanating from the rod end seal area, the shock absorber should be replaced.

There is no visual way to check the shocks piston seal without cutting into the cylinder. Once the piston seal wears shock absorption begins to go away and poor suspension control results. Another factor is valving which controls the compression and rebound rate of the shock absorber. The valving is precise drilled orifices placed in the hydraulic fluid piston controlling the dampening rate. Depending on the suspension engineers specifications the valving control rate is tweaked for the best overall suspension control. Road-race shocks are closer to neutral (50/50) on rebound and compression while drag-race shocks have a big spread. For instance the front shocks have a very low (10) percent rebound rate to help weight transfer with a (90) percent compression rate. For this reason installing a set of shocks that “look correct for fit” does not mean that they will restore the correct handling, in many cases they can hurt with poor suspension control. Finally the rubber mounting cushions or rod end sleeves wear and deteriorate from age. The loose fitting shock absorber mounting cushions cause rattles over bumps and rough roads while negating precise suspension control.

There are many conditions that affect a shock absorbers life as mentioned in the preceding paragraphs. One major factor that is often not considered is wheel/tire assembly vibration; the resulting up and down oscillations can quickly kill the shock absorbers piston seal and valving. If you pay attention on the interstate from time to time you will see a wheel/tire assembly that is bouncing up and down at a rapid rate destroying a perfectly good shock absorber. If the unbalanced situation is overlooked for thousands of miles suspension component and shock absorber damage is inevitable. Neglecting a wheel/tire vibration issue and the repair that could be as simple as balancing the assembly could cost big in the long run. Where you live can be a major concern in how quickly your shock absorbers wear, northern sections of US roads are peppered with potholes giving your shock absorbers a beating. By the time your Corvette reaches 60,000 miles it most likely is time to replace all four shock absorbers if you are driving on rough road surfaces. Southern Corvettes driven primarily on interstates can go upwards of 100,000 miles before any loss of shock absorber control is obvious. Something to consider, if you are expecting the best possible suspension control, 60,000 mile shock absorbers are not going to be in peak performance condition.

One of the most common ways to check shock absorber performance was pushing downward on the front or rear of the vehicle. The idea was to see how many times the vehicle went up and down after bouncing the vehicle. If the vehicle kept bouncing more than one time it was time to replace the shocks. While this method works on really worn shocks I prefer to observe the Corvette from another vehicle as it goes down the road. If you watch the vehicle closely you can see if the front or rear bounces three or four times after traversing a rough road surface. During braking watch for the back end bouncing after the vehicle comes to a stop. You can look at your tires for uneven wear across the tread. Really worn shocks let the tire bounce and then dig into the pavement creating square bald patches. The square patches will be evenly distributed around the tire. Keep in mind that as mentioned earlier a severe tire vibration will cause the tire to do the same thing creating small patches of wear. The difference is you will feel the vibration in the seat of the pants or the steering wheel which is hurting your shocks. Finding oil dripping out of the shock requires replacement. Always replace shock absorbers in sets of two front or rear preferably all four.

What Shock Absorber Should I Buy?

C5 Shock absorber prices go from $50.00 to $175.00 for Original Equipment replacement shocks. If you set the $50.00 shock absorber next to a $99.00 shock absorber the differences will be apparent. The low buck shock may or may not be a mono tube, at best it will a smaller diameter connecting rod and in most cases light duty hardware. The front shock lower mounting tube on lower quality shocks also has slots cut into the mounting bosses making them universal. While easy to install they are weaker when used in performance applications. Chances are very good that the lowest cost shocks will not be much better at suspension control than the shocks you are replacing. The inexpensive shocks smaller cylinder diameter lessens the piston area and requires less hydraulic oil. Less oil in the cylinder increases the temperature of the oil and diminishes the shocks effectiveness. The sign of a better shock absorber is a connecting rod and cylinder tube diameter similar to the OE shock. You know that you cannot go wrong with using the OE style Sachs shock absorber for street and mild performance driving. Corvette Central has three options the OE Sachs, QA-1 and Bilstein shocks. The QA-1 shocks are a great deal, large mono-tube cylinder with large diameter connecting rod for long term suspension control. They work very well on street driven Corvettes that occasionally visit the race track. Bilstein shock absorbers are also a good choice for the performance orientated driver. If you have had your C5 long enough and remember the original suspension feel, and it works for your driving style, replace the shocks with Sachs OE replacements.

Shock Absorber Myths

Many vehicle owners hear that shock absorbers will raise the vehicle or influence ride height. Back in the old days shock absorbers were filled with hydraulic oil, when the shocks were removed from the box the connecting rod stayed where the factory left them. Today when you pull a gas-charged shock absorber from the box they extend to their maximum length. This prompted many to think they have some influence on ride height, which they do but the effect is negligible. Nitrogen gas is pressurized between 300-350 psi in the tube not adding much lift to a 3500 pound vehicle. In simple terms if your C5 or C6 is lower at one corner or one end new shocks will not make it sit back at the correct ride height.

There are very few people that can drive your vehicle and say unequivocally that the shock absorbers are worn and need replacement. Race car drivers would be able to point you in the right direction concerning shock replacement, not the weekend warrior.

Any sign of leakage on the shock tube is bad, as mentioned earlier; you can expect a film of dirt to stick to the area near the connecting rod. If there is oil that is wet to the touch the shock is ready for replacement. It’s time to go through the shock replacement on a typical C5.

Rear Shock Installation

C5 Shock Replacement 01 (Medium)

Although I have the luxury of a vehicle lift, your shock absorbers can be replaced using a floor jack on the ground. I wanted to point out that I have an undercar jack stand applying light pressure to the driver side front end opposite the passenger side rear end. You can never be too safe when applying pressure to remove a shock from the opposite end of the car. Most vehicle lifts are set up for traditional vehicles with more front end weight which can get you in trouble. The front crossmember where the jack stand is placed works well for picking up the front end during shock replacement. A trick is driving the front tires up on a couple of 2×12 wood pieces to raise the front end enough to get the jack under the front end. Before jacking up the front end make sure you have the floor jacks cup centered on the aluminum crossmember not the oil pan or front spring.

C5 Shock Replacement 02 (Medium)

The same applies to the rear end when replacing the front shocks, taking a few minutes to assure the vehicle does not get out of control during the maintenance work. You can lift the rear of the Car at the same crossmember that the jack stand is applied to replace the rear shocks while leaving the front end and tires on the ground.

C5 Shock Replacement 03 (Medium)

The correct length shock absorber should not require any suspension compression during removal. In some cases the shock is slightly shorter and you can be surprised when the last bolt is removed. For this reason I always apply pressure under the lower control arm, taking the spring load off, to avoid a surprise during removal and the reason for the opposing jack at the front. The upper 13mm screws come out easily with this impact universal socket, especially the inner screw. Non-impact universal joint sockets work but they are always binding up during the task of removing or installing screws.

C5 Shock Replacement 04 (Medium)

The 24mm lower shock bolt and 24mm nut is removed then the shock is lifted up with a pry bar off the lower control arm. If you placed a jack under the control arm let the pressure off before lifting the shock off the control arm.

C5 Shock Replacement 05 (Medium)

While this may seem simple the shock is a tight fit when it is extended during removal. I usually compress the shock and move it down quickly to get it out of the upper shock connecting rod pocket area.

C5 Shock Replacement 06 (Medium)

This is how you will find most shock absorber upper nut and connecting rod shaft ends full of road debris and the occasional mud wasp droppings.

C5 Shock Replacement 07 (Medium)

You will be required to reuse the upper shock mounting plate, to make this easier I use a wire wheel to remove the debris and-or rust from the nut and shaft end threads.

C5 Shock Replacement 08 (Medium)

This is why I want the rod end threads clean; a special socket shaped as a double “D” is required to hold the shaft rod end while the 15mm lock-nut is removed. This socket came from Snap-On tools certainly a pair of vise-grips will work if the threads are clean. Sure you can try to spin the nut off with an impact wrench but the dirt and lock-nut make it difficult. By the way, you can spin the shaft of the old shock for as long as you want during nut removal. Do not attempt to spin the replacement shocks shaft during installation, the shaft can be spun off the piston requiring another new shock.

C5 Shock Replacement 09 (Medium)

New rod end cushions are supplied so the original cushions should be removed and any dirt cleaned off of the mounting plate.

C5 Shock Replacement 10 (Medium)

Our new Bilstein shock uses a universal style cushion, make sure the new washer is installed (cupped side up) and the cushion alignment raised area fits the mounting plate. The cushions can be turned over to utilize two different size raised areas. The raised area should fit inside the mounting plate rod end clearance hole. When the plate is installed with the upper cushion and the cupped washer (cupped side down) installed the upper nut is tightened until the rubber cushion begins to be outside the cupped washer. Too much squeeze will collapse the cushions and they will fail prematurely.

C5 Shock Replacement 11 (Medium)

To make the rear shock installation easier I use a piece of mechanics wire to hold the shock as close together as possible.

C5 Shock Replacement 12 (Medium)

The wire trick holding the shock together does help getting the shock into position. I also lift the rear control arm a bit to open the area between the toe-link and lower control arm.

C5 Shock Replacement 13 (Medium)

Once the shock is in place the wire is cut and pulled out.

C5 Shock Replacement 14 (Medium)

The upper shock mounting plate is installed and the 13mm screws are torqued to 22 foot pounds or 29.5 Newton meters.

C5 Shock Replacement 15 (Medium)

The lower shock mounting nut is torqued to 162 foot pounds or 220 Newton meters. While this may seem extreme the high torque is required to make sure the shock absorber mounting bracket has conformed to the bushing sleeve in the lower control arm. It may feel like the shock absorber bracket is tight when in reality the bracket is not tight against the bushing sleeve. If at all possible I try to torque the nut as opposed to the bolt which can have additional resistance during tightening.


Front Shock Installation

C5 Shock Replacement 16 (Medium)

I begin the front shock absorber installation by removing the washer fluid reservoir. Three 10mm hex nuts hold the reservoir in place.

C5 Shock Replacement 17 (Medium)

To access the passenger side upper shock mount I also remove the coolant reservoir, it is retained with 10mm hex nuts.

C5 Shock Replacement 18 (Medium)

Unlike the washer reservoir the coolant reservoir has a tab that holds the tank in place. The 10mm hex nut is loosened and the coolant reservoir level switch is disconnected before setting the tank to the side. You do not have to remove the hoses from the reservoir it will lay out of the way without harming anything.

C5 Shock Replacement 19 (Medium)

On the front upper shock mount I am using the same double D socket to rotate the shaft to loosen the nut. A 15mm wrench must be used to hold the nut from inside the fender while spinning the shaft. The shaft is rotated clockwise to loosen the nut from the shaft.

C5 Shock Replacement 20 (Medium)

Once the nut is loose enough a 15mm socket can be used to do the final removal of the nut.

C5 Shock Replacement 21 (Medium)

The 13mm nuts are removed from the lower shock mount and the shock is pried up and out to the side for removal.

C5 Shock Replacement 22 (Medium)

Like the rear shocks the front shocks are difficult to get out of the confined area. I collapse the shock and then pull it out.

C5 Shock Replacement 23 (Medium)

To ease installation I use this large Phillips head screwdriver to rotate the front shocks lower cross-shaft to about a 30 degree angle. This aids in bolt installation once the shock is in place.

C5 Shock Replacement 24 (Medium)

During installation the front shocks can be pushed upward and then moved over on top of the lower control arm.

C5 Shock Replacement 25 (Medium)

I always install the upper stud mount first centering the rubber cushion and putting enough pressure to hold the pieces in place. Once the wheels are on and the front end down on the ground I tighten the nut on the stud and install the lock-nut if provided. Like the rear shocks the rubber cushion should begin to squeeze outward beyond the washers diameter to avoid over-tightening.

C5 Shock Replacement 26 (Medium)

The 13mm lower shock mounting nuts are torqued to 22 foot pounds or 19.5 Newton meters.









C4 (84-96)

Corvette Rear Suspension Bushing Installation and Component Installation

By Chris Petris
Petris Enterprises

This is the third installment of a C4 suspension overview series. Click to view the first article, Click to view the second article.

In this installment, we tackle the rear suspension bushing installation and component installation.

So far I have covered all the C4 suspension disassembly and have the front suspension assembled. I have also shown how to remove the rear suspension bushings for urethane bushing replacement. Early on we discussed the

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availability of rubber bushed suspension components. Corvette Central does have the spindle rods available with rubber bushings (584150 Set of 4) or with polyurethane bushings (584090 Upper, 584108 Lower). Camber strut rods are also available with rubber bushings (584151 84-89, 584097 90-96 used/Reconditioned). Corvette Central also stocks good used certified suspension pieces that have gone through an inspection process to assure the best possible condition from a previously used piece. Whether you choose rubber or urethane, I will cover the required steps to install the urethane bushings and all the suspension components. Before we get started assembling, there are a few items to cover concerning the rear suspension.

Rear Suspension notes/tips

The 1984-1985 Corvette used an additional seal that was placed in the rear spindle knuckle to keep dirt, grit and water out and off of the bearing/seal assembly. I prefer to install this seal (Part #584157) in all C4 1984-1996 rear suspension spindle knuckles to keep the bearing and seals clean. The seal fits in the spindle knuckle and the yoke is machined in the same manner whether you have a 1984 or 1996 suspension assembly. There is less chance of water or dirt entering the area between the spindle bearing yoke splines and the bearings seal area.

GM used a ball bearing spindle bearing assembly with two rows of ball bearings for the least rolling resistance. The inner and outer ball bearing set is the same size, keeping them tight for many miles. Depending on the environment they have been through, they can go well beyond 200,000 miles. Hitting large potholes at high speeds will shorten their life, as will out of balance tire and wheel assemblies. The constant bouncing of the wheel/tire assembly beats up the ball bearings. The rear wheel bearing assemblies also have to handle torque application via a splined yoke to the bearing. Automatic transmission equipped Corvettes are typically easier on the splined connection to the bearing and may never experience the typical clicking of loose splines. Although I have seen nitrous equipped automatic transmission equipped C4s wear the splines quickly and the clicking begins. Manual transmission equipped C4s usually all end up with loose rear wheel bearings from on and off the throttle applications. A distinctive click is heard as the transmission is shifted from reverse to drive or vice versa as the splines wear. So far I have not had to replace a spindle yoke to tighten up the clicking splines. A new bearing assembly takes care of that. Proper torque sequence and a revised final torque are critical to long lasting bearings. GM recommends that no weight be applied to a new wheel bearing assembly until it is properly torqued. Installing the bearing and placing the C4 down on the ground for the torqueing procedure is a no-no. GM made some changes along the way concerning the final required torque specification. The 1984 service manual shows the spindle nut torque at 151-177 foot pounds. The 1996 Corvette service manual shows a recommended 164 foot pounds of torque for replacement bearings. To avoid premature loosening of the splines and loose wheel bearings, I torque all of the rear wheel bearings to 175 foot pounds with manual or automatic transmission equipped C4s. Of course you can use a big bar and hope for the best on reaching the required torque. If need be, go rent a big torque wrench for long lasting bearing life.




There is a rear toe link used to control rear wheel toe-in or out. The link spans across the rear of the suspension. It is anchored to the center of the differential rear cover with tie rod ends connecting it to the rear spindle knuckles. Unfortunately many suspension and steering pieces are replaced before this wearable part is replaced. The most obvious symptom of a failed toe-link is rear steer when you accelerate or decelerate. On and off the throttle moves the rear spindle knuckle changing the direction that you are traveling without ever touching the steering wheel. I don’t find many of the toe-links worn but it does occur. The rear steer can be very dangerous with a severely worn toe-link sending you from the inside to the outside of the lane. You can feel a loose toe-link by grabbing the wheel at the 3 o’clock and 9 o’clock position and see if it has any perceptible wiggle. If so, you have found your unintended steering culprit. The toe-link has inner and outer tie-rod joints. Most often the outers wear first. If so they must be replaced while a worn inner tie rod link will require complete link replacement. GM also used two different toe-link tie rod ends; early 1984-1991 #584119 used a male threaded rod end, while the 1992-1996 #584125 used a female tie rod end. Due to the equal length of an early or late toe link assembly they can be used on any 1984-1996 Corvette rear suspension system.

I have seen more than one rear anti-roll (sway bar) bar installed incorrectly causing the anti-roll bar to rest on the rear bumper aluminum support. The anti-roll bar then becomes the rear spring as it binds on the bumper support, keeping the rear spring unloaded. The anti-roll bar ends must go up as they wrap around from the pivot points, it may seem natural that they go down to connect while the rear suspension is unloaded. Once loaded the suspension travels upwards requiring the upswept anti-roll bar ends.

Now it’s time to go over the photos and shows how it all goes together.




The rusty hub and splines indicate a loose spline fit at the bearing drive hub. If you had a clicking noise when putting your C4 in gear or on hard acceleration you found the problem. Note the build-up of grease, dirt and general gunk around the bearing from the lack of the extra seal part number 584157. This hub is out of a 1996 Grand Sport. As you can imagine the manual transmission torque played a role in spline wear.


I’ll start with the anti-roll bar bushing (584101 stock, or 582308 poly) installation. One side of the anti-roll bar link and one side of the anti-roll bar need a bushing pushed into them. Note the copious amount of grease applied to the bushing surface that will be pushed into the link end. The 15/16 inch twelve point socket is used to receive the bushing as it passes through the links rod end. Go slow and watch for chunks of urethane as the bushing is forced into place. If any major amount of material is cut-off during installation the bushing will come out during operation.




The bushing sleeve is pushed into bushing next. A pair of Channel Lock pliers or the vise that was used to push the bushing into place can be used. Plenty of lube should be applied to the inner portion of the bushing and the outside of the sleeve.




This camber strut rod end is being cleaned up with a high speed grinder and 120 grit sandpaper roll. Like the front suspension pieces, remove just the remnants of rubber or any corrosion build-up. Removing too much material allows the bushing to move around and change suspension geometry. Too tight and the bushings will not rotate freely during suspension travel.




The urethane bushings push into the rod ends easily without any lube on the rod end bushing surface. Lube should only be applied to the inner bushing surface where the sleeve rides on the bushing. The sleeve is then pushed into the well lubricated bushings; the vise is used to make sure the sleeve goes in squarely.




Note; during the spindle rod bushing installation make sure to install one thin and one thick sleeve during bushing and sleeve assembly on the four spindle rods. The thick wall sleeve rod end connects to the body while the thin sleeved side connects to the spindle knuckle.




The differential will require installation to hang all the suspension/driveline pieces onto it. I decided to keep the original rubber bushings due to their new like condition. There are new urethane differential support bushings available (#584124) These are not available in rubber at this time. While this may seem counterintuitive with all the urethane bushings, it is for better ride on city streets. The rubber bushings will allow some flexibility over potholes while the urethane bushed suspension components maintain a tight handling feel. Once the differential is in place the bolts are torqued to 89 foot pounds. The two front torque beam bolts are torqued to 59 foot pounds. This is one of those places guessing how tight the bolts are can cause some real aggravation. Over-tightening the torque beam bolts can distort the differential housing causing seal leaks and vibrations.




Now we begin the assembly of the spindle rods to the spindle knuckles. This project required a complete suspension refinishing so I removed the spindle rod supports from the chassis. You may want to install the spindle rods into the support before placing the support on the chassis. You can also leave the support on the chassis. If you do remove it, torque the support bolts to 63 foot pounds.




The spindle rods are installed now, if you decide to install the bracket sans the rods. Beware the nuts can fall into the chassis if you let one go. They can be fished out successfully with a magnet. Remember the thick sleeve goes here or you will not be able to install the knuckle side of the spindle rod. Additionally the spindle rod will fit very loosely at this end if the rods are installed incorrectly. Another thing to remember: the shorter of the two rods is on top.




This project has urethane bushings in the spindle rods so we can torque the spindle rod nuts at this end to 63 foot pounds. I prefer to use the torque wrench on the nut side of a bolt and nut arrangement if possible. In this case I had to do the opposite. The urethane bushings allow me to position the spindle rods where they need to be during spindle knuckle installation. Rubber bushings would require me to assemble all the components loosely, then torque them with the vehicle at ride height.




This is my preferred way to install the spindle rods and support. Torque the spindle rods in place in the support then the support to the chassis. If all is well the spindle rods should move with some resistance after torqueing.




After doing a few of these C4 rear suspension restorations, you remember to install the spindle rod bolts into the spindle knuckle first. The bolts go towards the center of the Corvette. Adding the washers and nuts keeps them in place until the other pieces are assembled. If the caliper mount and backing plate are installed before the bolts are in place, they must be installed in the opposite direction. Just one of those trying to keep the job look like the factory did, the assembly things I believe in.




If you have a 1984 or 1985 you should install this secondary seal in the spindle knuckle. As mentioned earlier I install this seal in all 1984-1996’s. This is the Corvette Central part number 584157 seal that was discussed early on in this rear suspension installation segment. If you prefer you can leave the seals out on the 84-85, but they really do help keep junk off the bearing assembly and out of the splines.




Apply a light grease to the spindle yoke washer that is sandwiched between the yoke and bearing assembly. The bearing race and yoke are hardened metal alloys, the washer keeps them from working on one another and prevents bearing race damage. Quite often these washers are missing from a previous repair; they can stick to the old bearing and get misplaced during the assembly. Corvette Central has them under part number 584093 and they should be reinstalled or replaced if missing.




The 1984-1987 caliper mount and parking brake shoe assembly are installed onto the spindle knuckle and then the bearing assembly is set in place. 1988-1996 would have just the caliper mount installed before the bearing is put into place. Make sure no paint, powder-coating or debris is left on any mounting surfaces before the pieces are stacked together.




Now the bearing is torqued to 66 foot pounds with this Mac Tools specialty T55 long drive Torx bit socket. I make one pass at 45 foot pounds to seat the bearing and then do the final 66 foot pounds of torque. This socket works equally well with the axleshaft and yoke in place if you are replacing just the bearing assembly.




Before the yoke is slipped into the splines grease is applied to the auxiliary seal and the washer.




For the best possible bolt torque, I always clean the threads before assembly. Years of dirt and grease make the bolts feel tight when in reality they are not. In this case primer and paint have gotten into the threads. A 5/16-24 thread tap does the job quickly. A light application of oil can save many hours of work or yoke replacement cost to prevent a broken thread tap. If the thread-tap breaks off in the yoke, the hardened steel will make it very difficult to remove.



Threads clean and the seal surface polished now, the yoke is installed.




Now the washer and nut are installed. Check the washer for cracking especially in the center before installation.




The spindle bearing hub nut is torqued to 175 foot pounds with a 400 foot pound torque wrench. As I mentioned earlier, proper torqueing of the spindle nut is very important for long bearing life and keeping spline wear to a minimum. Also note there is no load on the bearing.




We’re ready for the spindle knuckle installation on the spindle rods. If the shorter spindle rod is on top and the thin sleeves are on the knuckle end all should go well. After the bolts are snugged up, they should be torqued to 107 foot pounds. A 15/16 inch wrench and socket work well, fitting the nut just right.




GM calls these camber strut rods spindle rods also. This can get you in trouble when it comes time to torque them. The washers with the raised center should be installed onto the inner sleeve before installing the camber strut into the differential housing bracket. This is where the camber bolt is installed and final torqued to 187 foot pounds. I always check this bolts torque after the alignment shop finishes. Back in the beginning we showed how the camber cam is marked so that the alignment will be close enough for a trip to the alignment shop. If you cleaned everything up and no longer have a mark for alignment, position the camber cam in the centered position. It should be fine for the trip to the alignment shop.




I prefer to connect the rear spring as the very last part of the assembly. With the spring disconnected, I can then raise and lower the spindle knuckle by hand making it easier to get the bolts to line up and go through the spindle knuckle. The outer camber strut rod nut is torqued to 107 foot pounds.




The axle shafts are installed before the toe-link assembly so the spindle knuckle can tip out during the axleshaft installation. The long 18 inch extension works well for the installation. The strap bolts are torqued to 25 foot pounds.




The toe link assembly was installed on the differential cover, torqued to 50 foot pounds and now the tie rod ends are installed in the spindle knuckle. Make sure the washer is installed under the nut to prevent the steel nut from digging into the knuckle’s aluminum material. The tie rod end nut is torqued to 35 foot pounds and then tightened until the closest opening in the castellated nut lines up with the cotter pin hole in the tie-rod end. I often find these nuts were not tightened properly and the tie-rod end comes out of the spindle knuckle without any effort. Although easier for me, the loose end will eventually wear the spindle knuckle and cause a rear steer issue. Also, never back off the castellated nut to insert the cotter pin. Always go tighter.




We’re getting close to that trip to the alignment shop. These new Bilstein shock absorbers from Corvette Central will enhance our urethane bushings and make this early C4 hold tight on the corners. The lower nut shown is torqued to 61 foot pounds.




This is how you can tell an early C4 from a late C4. This large upper shock retaining through-bolt is replaced with a stud mounted shock at the top. The early C4 shock absorber through-bolts are often not tight enough, causing popping noises over bumps. They should be torqued to 50 foot pounds. The later stud style should have the stud nut tightened until it reaches 19 foot pounds of torque. The upper plate that the shock stud goes through is torqued to 25 foot pounds.




The rear spring is installed, placing the shim pack in the same location they were originally. The shim packs are fiber plates with aluminum shims that sit on top of the spring cushions. If you want to lower the back end slightly all of the shims can be placed on the bottom. Start all the bolts and tighten them incrementally while watching the shims making sure the raised areas are going into the spring retainer. Once the spring retainers are seated, the bolts are torqued to 37 foot pounds.




The outer spring bolts can be replaced with longer bolts to drop the back end. This ten inch long spring bolt from Corvette Central replaces the original nine inch spring bolt. Note the long threaded area on the bolt for fine tuning of ride height. The jack is placed carefully on the spring end metal reinforcement to prevent damage as I raise it for bolt installation.




The urethane bushed rear anti-roll bar is installed loosely until the link ends are connected. Once the links are connected the anti-roll bar nuts are torqued to 22 foot pounds.




Finally the anti-roll bar links are installed into the spindle knuckle and bar end. Each bolt and nut is torqued to 30 foot pounds.




All of the pieces are in place. Now is the time to do a complete once-over, checking all the bolts and nuts for tightness. Rotate the axleshafts to make sure there are no strange noises and the differential is full of gear oil. If all is well, install the wheels and torque them to 95 foot pounds and head to the alignment shop.


1984-1985 Alignment Modifications for Maximum Positive Caster


Refinishing Suspension Components

Recently I have had a couple of questions concerning possible structural damage from the coatings that could be used on suspension components. The choice to powder-coat suspension pieces is entirely up to the vehicle owner, whether the pieces are steel or aluminum. I do not feel that powder-coating is a bad thing or detrimental to the component’s lifespan. I am not a materials or metallurgical engineer or think I know enough to say that the powder-coat process is safe or not. I do not recommend heating any metal that is used in suspension or steering unless it is done in a controlled environment by the manufacturer or by their recommendations.


The concern is the heat required during the powder-coat process. There is no definitive proof that the heat (400 degrees for approximately an hour) used in powder-coating will age the aluminum, weakening it. Many variables must be considered, shear strength and grain for example. Factory wheels and many aftermarket manufacturers use the powder-coating process on their wheels.

I mention powder-coat because it is popular; in our shop we routinely apply a urethane coating to all of our suspension pieces. In the past I have found that powder-coat can be a problem when it comes to keeping suspension pieces tight (torqued properly). If a customer prefers powder-coating, they are notified that additional steps must be taken during assembly and it will cost a bit more for the assembly.

Here’s why. I had a customer with knock-off wheels that continued to come loose. I tried every way to tighten them. After removing the wheel I inspected the surfaces. On the hub and wheel face it was apparent that the powder coat was breaking loose from the hub’s surface. As the material broke away the wheel would loosen. I consulted the problem with the owner and suggested that we remove the coating where the hub and wheel mated. After removal, the wheels stayed tight. Since then I am reluctant to leave the powder-coat on any surfaces that are bolted together and subjected to loading that makes the metals squirm around. During the painting process I also use the same method, keeping the paint off the mounting surfaces and then carefully torque each component. In race trim we have not had any loose component issues.

This is the third installment of a C4 suspension overview series. Click to view the first article, Click to view the second article.

C4 (84-96)

How do I install the new polyurethane rear differential bushings on my 84-96, as the bushing seems too large to fit?

C4 batwing bushing sleeveThe polyurethane bushings for the rear differential carrier or “batwing on a C4 measure 2 1/8” diameter on the portion that fits into the carrier hole.  When You press the original rubber bushings out, there is an outer “sleeve” from the bushing that remains.  This has to be removed as well.  One simple way to remove these sleeves is to cut them into a few sections with a hacksaw blade, then use a hammer and punch to drive them out.  Once that is done, the new polyurethane bushings should press in without a problem.