I hate to tell you but the engine will positively only fit one direction. The metal casing in which the engine sits only allows for the motor to point one way. I can spin the motor allowing the contacts to connect the same way to the metal housing but the driveshaft exiting the motor is still facing the same way resulting in the backwards running (if that makes sense). This particular F9 has an electrical pickup throuh the wheels. Like you mentioned though, I did switch the two trucks around thinking the same thing however was unsuccessful. For such a simple problem, I sure am stumped. Thanks for all the imput thus far, I do appreciate your guys' experience.