Oh crap, something just dawned on me. The Lehner motors have a 4mm shaft. I don't, for now anyway, have a way to put a plastic spur on my center diff, so I was just going to run the hardened steel pinions. I don't think that the 4mm pinions are available in hardened steel, are they? That's another consideration. Would the larger motors cause more wear on my pinion/spur gears. I may very well be stuck using metal on metal gears.