Just get 3908 difs, skip the others. I noticed the machining was alot better, than the lighter older difs. 3908 are the strongest stock difs you can get. Of course you can go farther with metal outer case and/ or more spiders, 6 spider difs are getting rare. You can easily spend $70-100+ a dif for bullet proof ones,

My best luck came from having a metal rear bulkhead, with 3908 difs, to keep it aligned and stop some of the flexing. But then they can bend...Mine ran a 4 pole 2560 Turnigy, brutal torque on take off. It would eat a dif quick. 2 poles are softer imo.

Eta lol, I have seen my old emaxx litterally smoke the tires (3.8 Talons) on pavement taking off. Nothing blocking it, just sheer wheel spin. I wished I would have video'd it lol. If you have 1 3908 dif, put it in the rear of the truck. The 3.3 might last awhile in the front, but not long in the rear. Been there, done that lol.