Different Kinda Clunk From The Rear??

[youknowmyname67]

I would say check the u joints my 99' tahoe had the same issue turned out to be the u joints.... didnt feel like a kick to the seat but a jolt and a clunk that sounded like someone kicked the exhuast.

 

[dz2a8r]

Kind of lat on the post but ive worked for several different manufacturers, and gm happens to be one of them. if im not mistakes the way we took care of the clunk noise your describing was to grease the splines on the drive shaft, but in addition to this we cut a piece of 5/8 hose to about 3/4 to one inch in length and put into the grease on th esplined end of the drive shaft.