As far as the gears striping, make sure you have a good tool when tighten the screws. Also set the mesh real tight till it is binding when you try to spin the spur gears backwards, then barely shift the motor till it sort of starts to spin free and leave it there. That's how I solved my problem and they are still going strong. Now when I look at the gear mesh, there is not any space between the gears. Before, I could see the space.