2002 Chevy Suburban sounds from drive train when in reverse

My suburban suddenly started making a loud sqeaking tyoe sound from the rear area when moving in reverse only with no breaks applied. The sound rate is in line with the speed at which you back up. It gets fater as you move faster. I can not determine if a u-joint would make a sound when turning in one direction versus the other or not. It's a pretty loud sound that almost sound like the sqeak of a large door hinge. Trying to dermine if u-joint, brakes, differential, ? Just not sure what could make a sound in reverse and not forward. There is no vibration or other symtoms beyond sound