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.
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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.

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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)

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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.

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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 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.



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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. Read more on “1997-2013 Shock Absorber Information and Replacement” »

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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 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.

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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.

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