Question about Sears Craftsman LiftMaster Chamberlain Garage Door Opener Wireless Keypad Model 976LM Security+

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Garage door only opens 4 inches then reverses and stops

Hi, my garage door opener plastic gear wore out. I bought the kit and replaced the gear and worm drive. The motor runs fine, but the door will only close 4 inches before it reverses backward 4 inches from original starting position. I've played with adjusting the up down limits until the cows came home.....but just keeps doing it. Is it time to toss it or is it something that can be fixed? It's a 1/3 HP. Thanks very much.

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You need to replace gear when the door is fully closed. then do your tweaking.

Posted on Jun 01, 2009

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Posted on Jan 02, 2017

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1 Answer

Garage door motor turns on makes noise chain does not move


I bet the Worm Gear is broken. Disconnect the power, remove screws on motor enclosure, remove housing, look for broken plastic gear pieces.
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The shaft on these garage door motors are not direct drive systems. You'll have to open up the box to see what the actual problem is. I have had stuff like this happen where a gear just slipped out of place.

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Make sure you put the black cup back on the end of the motor shaft and that it is pressed all the way on. Make sure the RPM sensor is plugged in. If neither of these are the issue, then you probably did not have the motor shaft pushed all the way back when you tightened the coupler after replacing the worm gear. Loosen that coupler up and from the front of the motor (opposite end in which the coupler is on) push the shaft back as far as it will go. Hold it there while you tighten the coupler back up and then try it.


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http://www.searspartsdirect.com/partsdirect/index.action?psid=58709328&sid=PSx20071217x00001a

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I have the same problem. I just removed the cover and discovered a nylon gear had been worn out. I found lots of shavings inside the cover. The nylon gear is beneath the exterior chain gear. I am looking for information on how to replace it, if I can find the part. If you decide to look at yours, unplug the power and remove the sheet metal screws securing the bottom portion of the cener cover to the front and back covers. Then just remove the upper screws from the center cover. Good luck.

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