as far as the spur gears goes.you have to have the pinion and spur gear lashed properly..put a straight pin in between the gears put the motor up tight against the straight pin and spur tighten it down then pull out the straight pin ..now the gears are almost perfect..had the sam thing happen with nitro trucks,,if the spur is to loode it will eat the gear..and also make sure youre slipper isnt to tight the slippers are very touchy..hope this helped a little..joe