The differential drives the vehicle down the road. A tremendous  amount of force is applied to the gears and bearings inside the case, even though the the gears and bearings are lubricated with a heavy duty oil wear does happen after hundred of thousands of miles, or can be damaged from extreme force being applied the gears causing breakage or misalignment. We are equipped to service the differential or inspect for wear and any noises the differential may be making and repair it.