The worm gear which attaches to the motor shaft meshes with the drive gear to spin the sprocket and drive the chain to open and close the garage door.
How to replace drive gear on craftsman garage door opener.
This diy repair guide explains how to replace the drive and worm gears on a chain drive garage door opener.
Replace a broken gear and sprocket assembly with the manufacturer approved replacement part.
If the gears break or strip the door won t move.
Follow the steps in this repair guide and video to replace the gear and sprocket assembly in craftsman chamberlain and liftmaster chain drive garage door openers.
This was a craftsman model 139 53976srt.