2000 Mazda 626 Rear noises

I am having the same problem. I checked the jack in the right rear of trunk and made certain it was tight. I suspect that I either have a loose muffler or tailpipe or broken hanger. Another possiblity I am considering is a damaged/loose rear shock.

Let me know when you find your problem and I will do the same. Dave in Denver

Hey there, I may have found our problem. When crawling under the back of the car, I found the flexible plastic bumper cover was loose and when tapping it with my hand, it made the same noises I (we) have been hearing. There are two plastic srews under the bumper that seems to be there to hold the rear bumper cover to the main impact bumper. I couldn't get them to tighten up, so I put in some rubber bushings (pieces of sorta-soft rubber pad) in between the bumper cover screa plate and the bumper. Seems to have solved the problem. Hope it works for you.
Dave