Bafang BBS02 Nylon Reduction Gear
This is the primary reduction gear for the BBS02 drive unit. You need to remove the motor and controller to change and it is about an hour long job.
To troubleshoot your BBS02 to see if the Nylon gear has failed (Click here to read the BBS02 troubleshooting article)
To repair a melted gear please (Click here for instructions on replacing the Nylon gear)