Ok, I am getting a small "Clank" from the rear end on normal take-off, but not all the time. I recently had some used 3.73's with a rebuild kit put it by a rear-end guy. Last week I had to fix a passenger side wheel bearing seal, it was leaking. What could be going wrong?
Take a look at your control arm bushings, u-joints, torque boxes, and ensure everything is tight. Also double check tailpipe clearance with the lip on your gas tank. I had one that rattled like a SOB off my tank and it drove me absolutely insane.