missing piece
 

I switched motors on my xmod and there was a piece that was left out. It was a piece from behind the motor, a yellow piece, is this needed?

if you have stage 2 motors you don't *NEED* that, because motors fit pretty tight into the heatsink. I put it back in, and it just stays in. I never have to remove it to swap motors. Without it, if you run head-on into something, sometimes the motor will fly out of the heatsink and disconnect from the drivetrain.

Did the missing piece help fix your grinding gears problem?