Tony, You said the wheel came off the base. is there something in the center of the wheel? If so you probably broke the axle. If not, then the nut may have come off. Tell me more about it. And when you are running your truck at full throttle, do you hear what sounds like a hicup from the truck then it goes faster? If so, you are shifting. If not, you can unscrew the set screw on the second gear. that set screw adjusts when you shift by decreasing or increasing the pressure on the spring in the shift mechanism. If you need more help with it, let me know.