I have noticed this sound coming from the rear of my 92 Z28. At first I heard it when I was going slow down the driveway, but today I heard the noise at 55 mph. The car sat for a long time before I bought it from the original owner, and has 32,000 miles on it. I am thinking it could be the u-joint. What do you think? thanks for any replies.

 

The u joint is a possibility, I would also check out the trans mout while your at it.