Ah ok, thanks for clearing that up. I'm waiting for info on the diff ratio and final ratios etc on the Genesis differentials and transmission, but in the meantime I checked out the Flux tranny and gears with 12 pinion and 60 spur, aimed at 30mph top speed and 3 second to get there, and it only drew 30 amps. That would be a nice setup, sort of slow but ah well.

I'm guessing monster truck differentials are somewhat similar, so I'm estimating that I should be safe with a low pinion like 12 and 60 spur.