Gear and motor problem

we connected our CIM to a toughbox. it seems that when we try to drive straight ahead it turns to the side.
it also makes noise from one side but we checked the gear and it seems fine.
any ideas about whats causing this and how to fix it?

Make sure you didn’t assemble one of the gears backwards. There are spacers that keep things from rubbing together the wrong way and making angry sounds.

You know how electrical parts like motors and speed controllers work because of magic smoke? And how if you let the smoke out they stop working? Mechanical parts like gearboxes work because of magic noise. Let too much noise out and they’re going to quit.

Check your 2mm key. That’s the thing that prevents the gear from rotating on the CIM shaft.

The gear is held on the shaft with the retaining clip. If you don’t have one of the retaining clip fingers in the keyway (the slot the key fits in), it’s possible for the key to fall out of the slot. Once this happens, the gear does not move with the CIM motor shaft … at least not as fast as the CIM shaft. Your motor will turn but your tough box output shaft won’t.

If one output shaft is turning (assuming right and left motors) but the other isn’t, your bot will turn.