Diffs/gear boxes are my main complaint with the car. I bought new diff boxes, and bearings. Put them in and the bearing was loose in the housing? All new parts... I've posted about this before and didn't get much feed back. I had to Sand down the diff halves a considerable amount to make them hold the bearing tight. Then the leaking.. With two shims inside the diff (manual calls for) it was too much friction, over heating the o ring and burning it up (yes even the clear one) and the leaking from the center because of the plastic spur which I fixed with some sealer. Also on the shimming of the diffs, I felt it could use some shims front to back on the ring gear, rather then side to side on the differential, but they dont make a shim that fits. They get a little play in the steering but its nothing crazy. Other then that if I had a couple build secrets the car is bullet proof, and a good ride.