Today, I was driving along, and all of a sudden, I hear this godawful banging/clunking sound comming from the rear. It sounds like metal banging against metal. So I thought maybe it was the strut mounts, like on my old Cutlass, but the difference was, it would do it even if I was going down a perfectly smooth road. And it was not constant either. Just all of a sudden it would do it. I went down a really rough dirt road, and I couldn't hear a thing! So I went home and sprayed all the sway bar bushings with silicone spray, and the it stopped, but I don't know if that had anything to do with it. It never did it before!

any ideas?

Sounds like you looked at everything but the brakes. Hint. Hint. Any noises if you bounce the back corners up & down.

agreed on the brakes, and the bouncing....

its possible that a heatshield could have come loose

I did the bounce test and I didn't hear or feel anything unusual.

I checked the heatshield, and all the exhaust hangers, they are tight as can be. Remember, The noise occured on a perfectly flat road too.
And I have been having some issues with my rear brakes making a slight rubbing noise, and sort of a metallic sound when i stop in reverse. It feels like they are only doing 1/2 of their job many times. Also, when I take off there is a SLIGHT little clunk comming from the rear area. Maybe this also has something to do with the brakes?

But do you agree that it doesn't sound liek a strut mount going bad? The noise was inconsistant with the bumps in the road. It was really loud too, like a piece of metal was breaking off and knocking another piece of metal. I drove it around some more and I haven't heard anything since.

If you don't see anything wrong with the brakes I'd have it checked out where they can put it on a lift & have a good look. Brakes & suspension problems need to be resolved ASAP. Our local Midas shop gives free estimates.

A heatshield on the brakes?

no..... a heatshield on the exhaust system, or anything else under there

oh, nope, all exhaust parts are tight. This was much harsher sounding than a loose heat shield would sound.

I seriously thought the wheel or something was going to fall off the rear that I pulled over ASAP. I was going about 25 mph if that helps

It started a little bit today. When I take off, there is a notiacle creek/clunk from the back, and over awkward bumps in the road, it will make a slight noise, like it wants to do what It did yesterday. All help is appreciated!!!