Chuck:

There are lots of things that can cause a loud pop or clunk in the RR. Here is a few of them:

Exhaust rubber hanger is broken, pipes are hitting the undercarriage.
Failed bushings
Loose sway bar bolts
Shock mount bolt hole broken out of the side of the lower swingarm (rare, but can happen if someone uses a short bolt for the shock rather than one that goes all the way through the swing arm.)
Broken shock
Lower spring perch clamp issue
Upper spring rubber gone (maybe)

You will need to jack up the rear end of the car and do a close inspection to find the cause, in short, everything is suspect. Sorry I can't nail it down further.

jorrell