I have a 1995 ford thunderbird V-8 when I put it in gear or/ while driving I let go the gas pedal and when I press it again I hear a clunking sound from the rear???

Yes, for the Carrier and Pinion Pre-load. Also a Crush sleeve on the Pinion. Make sure that the Diff has plenty of fluid. Raise each wheel and check for up-and-down play. In and out (pulling and pushing on the axle is ok) You may have a U-joint failing or a Pinion that is sloppy. Look for looseness in the U-Joints and fluid leaks and excessive play in the axles and pinion. You may need to remove the Drive line to get a good read. I recommend it.

Yes, Tracy is right. You have to have the drive shaft off the car to really check for sloppiness in the Universal Joint (U-joint). Depending on the mileage, it may need to be rebuilt. Find a driveline shop. If no one has previously been into the rear end, and the car was not abused, I would investigate the rear end, the "Pumpkin" as they call it, as a last resort.

One other thing is I've noticed that the clunk sound only happened when the car has been driven a while and not when only started driving.. Thanks by the way