The 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 rear differential bushings should press in without a problem.