On all the emaxx and tmaxx variations out there, are the internals all the same? They all appear to have the same case.

I have 3 sets of diffs. 1 from a pro .15 chassis (4910), 1 from a tmaxx 3.3 chassis (4907), and 1 from a brushless emaxx (3908)

There's a few variations but they all have the same 2.85:1 ratio and fit in any bulkheads.
1. The original Pro.15 and 2.5 unsealed diffs in the 2 screw outer cases.

2. The TMaxx 3.3 diffs. These have 4 screw outer cases to help keep the case from flexing and messing up the mesh. The bearing sizes and all the internals are different from the 2.5 version. The diff internals are the same as a nitro Revo and are sealed so they can be tuned with different weight fluids.

3. EMaxx 3903, 3905, 3908 Emaxx diffs. These use the same 3.3 outer case, ring and pinion and bearings as the 3.3 diffs. EMaxx diffs have a different diff cup with metal inserts. Also different spider gears with a bar in between them. These are the same as the ERevo diffs and are the strongest.

The newer ones have much much better internals. And the newer cases have more screws.

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.

Taking the time to shim the diffs helps them live too. Ditch the Teflon washer on the diff pinion and replace with metal shims, I believe the size is 8X6x.2mm. Pretty sure I posted a how to shim Traxxas diffs on another thread of yours but I can post it on it again if needed.

The 3908 diffs with aluminum cups can handle 6s without issue. The diff cups cost about 20 ea, but it is well worth it. If you use the stock plastic cup it will flex under extreme load and will shear the screws holding it to the ring gear.