I've got a rattle coming from the rear at all speeds and it's driving me bananas!
I first thought it might be the rear hatch but, it feels tight and I can't get any movement out of it. The sound is kind of hard to describe but, it sounds very similar to a loosely mounted spare tire. It's not that either though because I checked.
Any ideas?

 

Put someone in the back while you drive. Or you get in the back while someone else drives. Easiest way to isolate where the sound in coming from.

 

Crawl under it start looking and shaking stuff, loose shock, missing/worn out bushings on the shocks, sway bar, leaf springs. Check bolts, bumper,gas tank, armor,the little cover for the fill neck.

 

It sounds silly but check the sound bar too. Since it's plastic, you could have a loose wire laying against it that vibrates with the littlest movement.

Also, try popping off the interior trim in the rear panels and check for loose wires and what not back there