if you are talking about your firestorm 10t, it does have a sealed diff, so all you need to do is pull it out, clean out the grease, and refill it with diff oil... start with 1000wt and see how you like it, if it still unloads too easy, go up in Wt.. higher is thicker... the thicker the oil the more you will slow the diff action, you need some diff action to go around corners well, so too thick will detract from handling as well...