76Pitter

I had the vette out today and as I pulled away in first gear I got a sound which was like something had fallen off the rear of the car and it bucked. I shifted to 2nd and got the same sound and it bucked again. I immediately pulled over and looked underneath the rearend but could not see anything amiss. When I put it into first gear to try and drive the gear engaged but the car would not budge. I went into reverse and backed up a couple of feet then re-engaged first gear and it drove fine. When I got up to 40 mph I began hearing a tapping coming from the rear end. I babied it to my mechanic and left it with him as all I can think that would make this noise would be bearings or U-joints. He found the clip loose on ujoints and tightened it and said he couldn't hear anything on the test drive. He said the bearings appeared fine. Anyways I pick up the car and right away I hear the noise again at 40 mph. I guess he couldn't distinguish it from the exhaust noise. Anybody had this problem or know what it is? Never had any problems of this sort until today.
Thanks for any advice on the subject. Mark.
76 L-82 4 speed. 54,000 miles.

Phlash

I would suspect a spider gear or shaft problem. Unfortunately the only way to know is to take it apart. Before you do, take a small magnet on a flexible shaft and try to see if there is any metal loose in the differential by removing the plug and inserting the magnet to the bottom of the differential. Fine particles are normal, but in chunks is bad news.

Phlash
72 BB Roadster

Gordonm

I just had my rear end break on me at the strip. It locked up solid. Make sure it is not the ujoints before removing the rear. If it is inside the rear you have to remove it and take it apart. If you suspect spider gears it will have to come apart. Mine broke all the ring gear bolts. I doubt that happened to you but I would first check the ujoints. They sometimes look good and are still bad. If you have not replaced these in a while it might be time to do it know.

76Pitter

Thanks for the input. I had the car out today and did the standard tests. The noise is only present in 4th gear at 1500 rpm and up which would indicate problem with driveshaft or u-joints. I didn't get any thumps when I did the accelerate and off in 4th which is supposed to tell of bad u-joints. I will check the joints and driveshaft tomorrow. Hopefully its as simple as losing a weight and unbalancing the driveshaft. In any event there have been no more lockups or bucking. If it is the u-joints it will just mean early storage and get at them in the spring. Thanks again.