Check out my profile for my ongoing saga of chasing down noises in the rear end. Most recently, I turned on the car radio while working on the car and could hear a clunking emanating from the ghost spare tire. I could only hear it because the bass was way up and I have a sub in the back, and I was under the car. But it gives me a new series of tests to run, looking for this noise.
Basically, noise in your back end under various conditions could be anything. Make sure everything is tight, then do it again. Punch things with the fatty part of your balled first and listen to the noise. Tug, push, and twist on things. You gotta test everything at every angle. Take out everything in your trunk., and the spare tools, and the foam then test and bang with fist. Have a little person sit in the back and point at the noise. It's in the back end, but it's not guaranteed to be suspension.

Edit: and Godspeed you poor SOB