Driving home from our annual car show this past weekend I noticed the rear end started to produce a loud clunk when shifting into Reverse and Drive. After troubleshooting the next day I found the rear differential snubber upper bushing cracked and laying loose in the frame bracket. What is puzzling, the top washer looks to have been over tightened or deformed from driving and shifting gears in the automatic.

Has anyone ever experienced the top washer bending and deformed from the top of the bolt? The snubber bushing was replaced with a kit from a corvette vendor 5 years and 12,000 miles ago and installed by a local mechanic. The only thing I can think may have happened, the mechanic used an air wrench set to 100 lbs or so and over tightened the bolt or it worked its way to deform the washer from shifting gears?

I purchased a new snubber kit from one of the corvette vendors and installed myself it tonight, tightening to 65 foot pounds, according to the AIM and Shop manual torques specifications. Tokk about 1.5 hours. I used the new washers that came with the kit. The top washer looked slightly thicket than the old one and possibly a grade 8 or hardened steel to match the bolt. I read some people used either the original lower or thicker lower large washer. But, just wondering if anyone else has used this kit SU42B and used the enclosed washers with no issues. Or should I have tried to find a thicker upper washer? Or do you think the enclosed washers with the kit work just fine?

Thanks

Old upper washer and bushing.


Cracked bushing


Side picture of cracked bushing and washer


New Stubber Kit


Newly installed kit, upper bushing, washer and bolt torqued to 65 foot pounds
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The distortion of the washer could have been caused by the differential mount moving around while under load. The mount you took out and your replacement mount looks to be poly. If it is, that may be your problem. The ploy mount is not as thick as the original rubber mounts. I put a poly mount in my 66 and the rear driveshaft universal joint used to hit the fiberglass tunnel when I had a passenger with me. It was real noticeable when I drove over a speed bump. I don't want to start a war over poly, but that was my experience. Jerry

 

Thank you for the reply "Tampa Jerry". That is puzzling, the websites that list this bushing kit mention it to be OEM GM licensed and no mention of poly. The part is carried at several vendors? When taking the part out it appears to be softer than poly and rubber like? I'll have to contact the vendor and start questioning the kit. The issue I see with the kits is the washers are much thinner than originals. Unfortunately I do not have the originals, but talked to another Vette friend locally who sent me pictures of his that he replaced. I plan on trying to find some hardened steel washers, remove the washers received with the kit and install replacements.