Man, been a bit since I messed with this but you may have to avoid the modern tammy tank electronics if your running separate gearboxes to each sprocket? The modern tammy tanks have a different way of propulsion with one motor for fwd/rev and one to turn. I'm sure you can get around this but I'm not the person to tell you how. If you want momentum on your forward/reverse drive get one of the DMD/MF from the KV or IS-2 tank kits. If not grab a Pershing unit (includes a small light unit,) If your trying to use a stock tammy recoil unit just have to avoid the tammy 105 Sherman due to it doesn't have recoil on the MF board.