971 uses the AM guts, makes custom plates, mods the gears and adds a hex shaft with pot attachment. If you go pneumatic make sure you tune the dog gear alignment before you do a final tighten. Always good to break in the motors and the transmission and make sure you use lots of lube on the gears.
Always check the main pinion for wear and tear. If your robot is geared fast and does high speed direction changes the pinion can have a catastrophic failure. Here is our tech note
http://www.spartanrobotics.org/conte...ed-pinion-gear
