Is it a clunk or a rattle. Mine sounded like a can of change over rough road. Head rocks in lower rear suspension, but that didn't stop noise. Ended up being shield on rear brake.
http://www.camaro5.com/forums/showthread.php?t=151206
There are videos on last couple pages are old. Here are better links
http://s188.photobucket.com/albums/z...amaronoise.mp4
http://s188.photobucket.com/albums/z...tlingpart2.mp4