[Espeefan]

Are you sure you have a good battery, freshly charged? If yes, then double check your motor pinion to transmission spur gear mesh. If that looks good, then loosen the motor from the mounts completely, and roll the truck on the floor to feel for any drivetrain bind. Try all three gears, rolling by hand. If all feels well then either the motor is weak, or the MFU could be causing your problems. I've been told the Tamiya MFU limits the power to the motor, to prevent drivetrain damage. The solution is to run a seperate ESC, and hook the MFU to the same channel with a servo y-harness, just so the MFU will match the sound to the ESC function.