Got back from the hobby store.
A little how-to on making a transmission:
Start out with a motor of your choice, square styrene, CA glue, and all your tools.
First, cut two lengths of the styrene.
Next, cut out the top of the styrene and drill two holes that match the holes on the motor. Cut some XMod screws so they don't interfere with the motor's armature. Put it all together:
And now it's on to the gears. Part II comes later. Also, I realized I can't work 4WS into this in 11 days. I would need whole new front end for an XTruck for the steering to function, and I just can't work that out.
Sorry.
-LM