If yours is a belt drive you need a kit like this https amzn to 2zqns.
How to replace garage door opener gears.
So if you suddenly find that the motor on your garage door opener sounds like it s running but the door is not moving checking for worn gears is the first thing you should do.
Located at the top of the motor unit the gear and sprocket assembly drives the chain that opens and closes the garage door.
Https amzn to 2uwvnkj i m working on a chain drive opener.
Fortunately the repair is neither difficult nor expensive and it should only take an hour of your time.
This video from sears partsdirect shows how to replace the drive and worm gears on a chain drive garage door opener.
This gear kit on amazon.
Before doing any work on the garage door opener you must unplug the opener to guard against the possibility of an accident.
Step 1 unplug opener.
This was a craftsman model 139 53976srt.
If the gear and sprocket assembly breaks the motor runs but the door won t move.
The worm gear attaches to the motor shaf.
This diy repair guide explains how to replace the gear and sprocket assembly on a chain drive garage door opener.