Make sure the one way bearing is not locked on the shaft. Turn the spur gear by hand in one direction and see if the truck moves. Then spin the spur gear the other direction. One direction should make the truck move forward and the other direction will spin free and the truck tires should spin. If it does then the one way bearing is lock to the shaft. If it is then free it and replace the one way bearing. Also check that the brake is releasing the breaks. With the truck on the ground and not running use the radio and press the throttle forward and see if the truck rolls freely.