I too have had a horrible time with the magnum. The first thing to go is the spur gear. Why is it plastic to begin with? If you change it to the steel upgrade the next thing to go will be the diff, as they are the next week link in the drive train. After you change them to the "upgraded cnc gears" you will then start to shear off the pilot shaft at the end of the crank. Why? because now that all of the gears in the drive line are finally grabbing the energy from the motor has to go somewhere, which causes the chassis to flex creating a bind between the pinion and spur gears breaking the next weakest link the pilot shaft. I only found this out after I sheared the second pilot shaft, of which I had my LHS check my gear mesh before running. We got to checking it out and noticed that the chassis has a lot of flex around the hole where the flywheel protrudes through it. We could see that the flex was causing the gears to bind. Thus causing the shaft to shear. A major flaw in design. Thus making this a Major Piece of CRAP!!!