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

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Garage door gears misaligned

Someone hit the door with a fork lift and now the chain keeps coming off the sprocket. I can align everything when the door is open or closed but it has horizontal movement halfway through the travel. It looks like the torsion spring is shifting it's shaft when under load but I don't know how to prevent this. Any Ideas?

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I got it... I moved the take up wheels that the cable wraps around to their outermost position and it's keeping the shaft from moving. kinda scary though, I don't like working around those torsion springs.

Posted on Feb 19, 2009

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1 Answer

My Lift Master garage door will not close. It makes the closing noise but the door does not slide down. Whcan I talk to to fix this?


Sounds like you have a chain drive garage door opener and you hear a humming sound when you push the wall console. The motor is running but the chain does not move. You need to replace the gear & sprocket assembly.

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I put a new gear and sproket on my sears lift master. It works, however when i press the garage door opener it goes one way for a few feet


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Oct 17, 2013 | Garage Doors

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HI, AFTER REPLACEING PLASTIC GEARS IN SAERS GARAGE DOOR O[ENER, OPENER WILL NOT GO THROUGH COMPLETE CYCLE. WHEN BUTTON PUSHED TO OPEN, OPENER GOES INTO CLOSE CYCLE AND HITS STOP BOLT. ATTEMPTED TO ADJUST...


Loosen the chain enough so that you can remove it from the sprocket above the motor unit. With the door closed run the motor until the sprocket turns clockwise and stops. With everything attached replace and tighten the chain. Some adjusting of the up and down limits will probably be required.


Mar 28, 2011 | Sears Craftsman LiftMaster Chamberlain...

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The chain came off my Craftsman 53920 garage door opener. How can I fix this problem?


When a chain comes off it is an indication of another problem. The bearing on the sprocket shaft is bad and lets the sprocket lean forward and the chain pops off. The part number you need is 41C4220A Gear and Sprocket Assembly. The chain can be loosened by the nuts on the trolley.

Sep 11, 2010 | Sears Craftsman LiftMaster Chamberlain...

1 Answer

My garage door chain came off, i put it back on


Loosen the chain enough so that you can remove it from the sprocket above the motor unit. With the door closed run the motor until the sprocket turns clockwise and stops. With everything attached replace and tighten the chain. Some adjusting of the up and down limits will probably be required.

The chain normally comes off when there is a problem with the sprocket and gear assembly. The bearing goes bad and lets the shaft lean towards the door and the chain comes off. If this happens again you will need to replace that assembly which is part #41C4220A and is available at any good door service company.


Jul 24, 2010 | Sears Craftsman LiftMaster Chamberlain...

1 Answer

I just replaced the gears in the opener and now the door stays open about 2 ft. When I hit the button it closes about 1 ft. and returns to it's original position...


Loosen and then remove the chain from the sprocket above the motor. Run the opener until the sprocket has turned in the counterclockwise and stopped. Now with the door in the open position replace the chain on the sprocket and tighten. This will get you close and minor adjustments to the up and down limits may be needed.

Jul 23, 2009 | Sears Craftsman LiftMaster Chamberlain...

2 Answers

Lift master garage door opener. Motor makes noise when switch is hit likes its running but chain/sprocket doesn't move and the door is stuck open. Chain is on sprocket. Not sure if the motor is frozen? ...


I had the same problem. Took the cover off of the opener and found that the gears were stripped on the unit. Motor was fine. You can order gear replacement kit for the unit. They are a plastic type sprocket and worm gears. The kit comes with spindles and all necessary clips. You have to take the unit off the ceiling to replace the gears, but the process if very easy to do. Parts kit about $40 on line, much cheaper than a new door opener. Total process took less than 2 hours, including getting the unit down and back up again.

Jan 24, 2009 | Sears Craftsman LiftMaster Chamberlain...

1 Answer

Press button to open garage door, doesnt work


may have stripped gears. take off light panel and look inside. white powder. bad gears. repair if yu are handy, if not, buy new unit.

Jan 19, 2009 | Sears Craftsman LiftMaster Chamberlain...

1 Answer

How is the chain supposed to be aligned


sync the motor. the gear kit tells you how. get motor up and position trolley near motor, assuming you left chain/cable attached to trolley). Get motor up by running motor and then pushing button again. if motor reverse, let it run and it will stop in up position.

Jan 17, 2009 | Sears Craftsman LiftMaster Chamberlain...

1 Answer

The chain has come off the sprocket.


The gear/sprocket assembly needs to be replaced with part # 41C4220A. The top bushing is worn out that is why the chain fell off.

Dec 31, 2008 | Sears Craftsman LiftMaster Chamberlain...

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