Help with build a strong diff ! What to use?

[ssspconcepts]

The hybrid bulks should work fine. I don't have a G4 but I would assume the G3 Maxx and FLM hybrid bulks would fit just fine. Especially considering that the 3905 basically uses the same bulks as the earlier Maxx version. Therefore it is safe to say that the G4 will also work fine with the earlier bulks (to include FLM hybrid bulks).

If you already have purchased the truggy diffs...I think you could keep them and just use a pinion gear that has a +2 or +3 tooth count and you'd be fine. Sometimes this is the best option anyway given the size of the large Neu 1515 series motor and the resulting limitation it imparts on what pinion sizes you can use with the stock motor mount (or most aftermarket motor mounts for that matter).