There seems to be a grinding sound coming from the rear driver rotor or break. on 2004 Dodge Viper

while the car is slowly moving forward, I can hear what sounds like there may be a rock caught up somewhere, there seems to be no damage to the rotor and the pads all all "meat" could this be a break issue or is it the diff?

Asked by for the 2004 Dodge Viper
check the rear bearings - check the fronts while your at it.