If you take the diffs apart and there is a problem you will see metal and stripped gears. In a diff you have 6 gears on the MT a ring and pinion, which will be the first ones you see when you take it apart. Then once you take the ring gear off the cup you have 4 spider gears in the cup. You need to make sure you check all of them. Since you have the RTR and has the poor pot metal ring and pinion if they are bad make sure you up grade to the heavy duty like comes on the SS.