Originally Posted by Steve_Alaniz

Banebot has a problem with their transmissions. The tolerances are off... Sometimes the motor shaft pushes up against the case of the transmission... I have 4 and two of these have that problem. I put a small washer on all 4 screw between the motors and the transmissions. It backs the motor shaft back just a bit but that's all it needs. This creates a gap around the motor to transmission joint, but I can tape that and the unit runs smoothly. If that's not for you, you can try making a spacer gasket with just thick cardboard.
I've done both and they've worked perfectly. I went to the washer because... I'm Lazy... It's a gift. (If you want to find the most efficient way to do something... put your laziest person on it.)

Hope this helps

Steve