It was like most people said, rear diff bushings. I didn't have time to change all 4 so I just changed the bad ones without dropping the diff. It is a huge PITA to take those out but it's doable. No more clunking, the ride is smooth and shifting is smooth. Thanks all for help! Anyone having the same problem check your diff. like someone told me go underneath the car and push up the diff right where it meets the ds. Mine moved about 1/4 inch. That's all that's needed for that ugly clunk!
Follow Ups
Rear Clunk Problem Solved! - YlwPrlZTT23:13:04 09/19/08