My truck has been in the shop 4 times for this issue, and they have been unable to diagnose the problem.

My rear passenger side tire area makes a metal-on-metal scraping noise that can be heard when moving between approx. 5 and 15 mph. It cannot be heard at higher speeds. It only happens after the vehicle has been sitting for a period of time. While vehicle is being continuosly driven, noise cannot be heard - even after being stopped at a traffic light or stop sign. Noise goes away when turning right, but can be heard when turning left. Cannot be heard when backing up. Any ideas?