Gearing?
 

From what I've read the x4 gearing possibilities are:

pinion: 13 14 15

Spur: 29/16 30/16 31/16

Diff: ??? How many teeth are on the diff crown? Is it changeable?

And what's the outer diameter of the tires?

Thanks

Sorry I never counted the number of teeth on the diff crown BUT they are they same front and rear.

As far as wheel diameter it changes pretty quick because they are foams.......and I don't have a new one to measure for you.

I do believe a 12 tooth pinion would fit on too.