"clunk" somewhere

[MyGreenZ]

I've got a '96 Z71 pickup that has a somewhat misterious clunk when I let off the throttle and then get back into it. The most noticable time is when going over a large hump such as a bridge or railroad crossing. I let off to slow down and the accelerate off of it. This occurs at low speeds, it's not like I'm hard into the throttle. The clunk sounds mid-to-rear of the truck so I originally thought U joints, but nothing seems to have any play in it as far as the U-joints go. There is a little play on either end of the driveshaft but not in the actual U joint. Should it have a little play? suggestions?... Thanks

[MrShorty]

See response in http://www.gmtruckclub.com/forum/showthread.php?t=10536