That's the kind of motor and gearbox I'll be going with but I'll just be using one and running it through the differential. The one I'm looking at is the one that rivet counter posted the link in his first post above. It's the last link in that post for the macro drill. That looks perfect for what I want to do and should drive the differential just fine. Rivet counter advises, and I agree, to get the differential first and then decide on the motor and gearbox because they come in different ratios.