I tried to find the klunk for 2 years. I've been told it's a broken shock, a bad control arm or panhard barbushing, a bad transmission mount, a loose jack or spare tire, and a bad rear end. Its a faint klunk, usually heard when driving over bumps, which sounds like it comes from the right rear. Lot's of other people have reported the same sound, and said it went away with a rear-end replacement. So I planned on driving 'till the rear end blew completely.

During a throwout-bearing replacement however, I went to remove the torque arm and noticed the two bolts holding the torque arm to the rear end weren't that tight. I'd guess they were torqued to maybe 15 ft-lbs or so. When I put the car back together I torqued the hell out of them. No more klunk. Tightening two 21mm nuts, that's all it took!!!

I just thought I'd pass this one on and hope it helps someone else.

 

sometimes thats just the way it is. I had some really bad lash one time in my oldmustang. brought it in just for a diagnosis. turned out a set screw on each side of the driveshaft was loose. they charged me 80 bucks [:@]
i only wanted a damn diagnosis