I read several posts by several different people who said they have experienced loud bangs when driving, usually slowly.

Yesterday I was going at a crawl through the mall parking lot.. there was a guy walking next to me.. All of a sudden there was a real loud BANG that came from the rear of the car. It sounded like someone slammed the trunk hatch, only nobody did of course. It wasn't a backfire I don't believe.. it was more of a metallic banging sound. There was absolutely no vibration throughout the car, just the noise. I was like what the heck was that... the guy walking next to my car kind of jumped and started looking at me and the car.. I rolled down my window and asked him did you hear that? He says yeah that was certainly loud enough to get my attention! The look he was giving me was like he thought the car was going to blow up.. I was just like oh well whatever, thanks, and drove off. If I didn't read on here previously about the same thing, I probably would have been worried as hell too. You'd think if it was the tranny I'd probably have felt something since mine is manual.

So how many people have experienced this after all? Any idea what on earth it could be?