I have finished building my kit but yet to drive it , with the experience i have seen some have with the diffs, after building mine i realized that the inner and outer movements of the cup drives were way too much so i shimmed both sides under the big gears (not sure right now of the size shims used ) but it took out most of the play without binding up the diff. i hope that will help in not stripping the gears.the only other thing i would like to find out is, has anyone had any problems with the ride height on the front of the car using the box setup.