C2 Rear Thumping noise

[Jerry L.]

I have a thumping noise radiating from the rear drive train. I have checked all the normal suspects: universal joints, bearings and driveline. The thumping noise is there with the wheels on and off the car you can feel the thumping in the car body with the car in gear, on jack stands and the RPM up. I now suspect a differential problem and would appreciate any suggestions on how to determine if that is the issue or if there is something I have missed.

Background on the car is that I have had it since 1978, has 70K miles on it and I have only put about 8K of those miles on it over the years. The rear bearings have been replaced, but the rest of the rear drive train has not been touched.

Thanks in advance,

Jerry

[William C.]

Re: C2 Rear Thumping noise

First pace to start is by defining the conditions under which the "thumping" occurs. Acceleration, braking, turns (left or right) one easy place to look is with the support holding the front of the differential. Common for these to wear or bolts to loosen allowing the u-joint to hit the body. Which rear bearings were replaced?

[John H.]

Re: C2 Rear Thumping noise

The thumping noise is there with the wheels on and off the car you can feel the thumping in the car body with the car in gear, on jack stands and the RPM up.
Jerry

Jerry -

With the car on jackstands (wheels on or off) and the suspension hanging in full rebound, "thumping" from the rear is perfectly normal with the driveline operating; it's the half-shaft U-joint trunnions grounding out against the yokes twice per revolution. If you're going to run the driveline with the car on jackstands, you need to jack up the trailing arms to get them closer to their normal ride height position in order to eliminate the interference.

[Jerry L.]

Re: C2 Rear Thumping noise

John,



Jerry