So i'm running the stock differentials that came with my 3906, And I have since put a brushless system in it. For the most part, the drive-train holds up great but i've been messing up differentials on 4s when i beat it hard enough. I was wondering if the diffs/diff cups, in the... 3908 is it? Are any stronger than the 3906's. Would it be a better investment to go aluminum cups or do you think the brushless diffs will hold up?