[jhautz]

Stock Emaxx diffs are 13/37, the regular HB diffs are 13/43 and the pro are 10/43.

If your running a transmision you want the regular. The pro have a lower gear ratio and it forces you to run a really big pinion to compensate. Even the regular HB diffs are a lower ratio than the stock maxx diffs so you will need to run a slightly bigger pinion. The pro are even lower and you will run out of room on the motor plate for the really big pinion.

The pro are more geared toward trucks running a center diff.