Recently, my car started making a metal-on-metal clanking noise when I go over bumps. It seems to be coming from the rear of the car, I think on the left side, but it's hard to be sure. It almost sounds like something has worked itself loose and is getting bounced around. At first, I had myself convinced that it was something in my trunk, but I've double and triple checked that there's nothing back there that could be doing it. Whatever it is doesn't seem to be affecting the way the car drives at all, but obviously I'd like to track it down before it causes a problem. Ideas would be appreciated - thanks for any help you can provide.