I was in traffic today and (I thought) my brakes started squeaking, that's what it sounded like. Then I got off the highway and I was goin about 40mph and it sounded like a constant brake squeak. So I stopped turned around and drove again and no sound driving or hitting the breaks. Parked for about half hour then went to get dinner. I was sitting at a red light and heard why sounded like a squeaking belt but it was coming from my rear end. Speed up it gets louder slow down quieter. So i stop on the side of the road turn around and no noise. Any ideas what's goin on?