Check all of your control arm bolts and torque them per the spec.

 

My 08 JKU did this from going from reverse to drive and around slow turns. I would get a loud clunk clunk noise. In my case it turns out my rear differential was shot so I had to replace it.

 

Love reviving older threads. one thing I have noticed is when parked on level ground, in park with parking brake on, if I crawl under keep and rotate rear DS it will turn a bit in both directions. Then there will be a click/clunk and it will stop or at least reduce to about 1/8" in both directions. Any ideas why?

 

Bump to revive!!!