I can recreate it while just sitting in the garage if I just push up and down on the rear of the body. But it happens on any kind of road, even no noticable bumps, its pretty annoying. Anyone have any ideas on where to start? Seems to have just started recently. Only thing I have changed in the past year is a built 4L60E, chromemoly driveshaft, and strange 12 bolt with 4.11's. Everything should be snugged down suspension wise.

 

In my case it was the rear control arm bushing. Tried greasing them and never did last long. Finally replaced the bushings and all is well. Sometimes sway bar bushings will do this as well.

 

It could be a sway bar bushing. All my ends are QA1 rod ends, so nothing to squeak there. Could that be a sign that I over/under tightened the swaybar end link.