I have a 94 Corvette coupe w/75K miles. No engine or suspension mods that I am aware of. Had the car about 18 mths; not a daily driver. The car appears to have had an easy life. I use it as a weekend cruiser; no racing, autocross etc. There is a clunking noise that I & mechanics think comes from the rear suspension; the noise comes from both sides, typically one side at a time. 2 mechanics, 2 body men & 1 allignment specialist have checked the car & haven't found the problem. If the car is put on a lift, such that the rear whells hang freely, the noise stops for 1 to 2 days & gradually returns. Driving about 10 mph over a shift in the pavement of less than 2" can produce the noise. The sound is similar to a bad shock or what you would hear if you had a 2 x 4 in the bed of a pickup & lifted one end 2" and dropped it. The noise is heard at least thru the 50 mph range, but never happens on very smooth pavement at any speed.

I have driven with the hatch open & it still makes the noise. I have removed the spare & spare cover & it still makes the noise. I've had the car alligned. Exhaust appears to be solidly mounted. I had the shocks, U-joints (all six), and rear spring bushings changed. I also tried lubricating one rear spring bolt with teflon & silicon to see if it quieted one side; no luck. A mechanic disconnected one side of the sway bar & said there was no need to change those bushings. No one has found any slack in the control arms or strut rods, but the bushings in the control arms, strut rods & sway bar have not been changed.

Advice & recommendations relative to diagnosing & correcting this problem requested.

 

gee... did you check wheel bearings? I doubt it... but ask'n none the less.

To remove the ujoints means taking apart major parts of the rear end... so I hope when they did they woulda fixed any loose bolts.

it is possible that a control arm bushing is bad... very possible. The loads on them are much greater than anything a man's hand can emulate.

 

Thanks for the insight; reasonably certain loose bolts have been eliminated as everyone who looked at it was attempting to find the noise. Did not check the bearings; would they make the noise only when there was a bump; there is no hum or vibration; is the 75K mile mark about where you would expect them to wear out, & would both rear likely give out at the same time?

Relative to the control arm bushings, I don't think there are OEM bushings for all of them; believe whole control arm would have to be replaced. That leaves after market which I believe only sells Poly bushings; I read a thread that said Poly rear & rubber front was bad;
Does it really matter if I don't race or autocross etc.; I do run her up to 120 plus for very brief intervals. Also how difficult is it to remove & replace bushings that were not designed to be removed; do you know where I could download instructions for the mechanic, or is it that big a deal.

Again thanks for the help!

 

My rear bearings only last about 66,000. The car is now on it's third set and I still get noise.

 

Here's a crazy thought, but remove license plate & gas filler plate & look/feel around for something loose there, ck antenna motor, odd ball stuff like that.

 

I think you should take off the rear plastic inner wheel well covers. You can check that the bolts for the rear subframe are tight, antenna and charcoal canaster. It is not a big job and is a good possability