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

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The chain has come off the sprocket.

How do I get it back on?

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

Posted on Jan 01, 2009

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The chain sprocket does not move but the moter runs

I think you need to replace the drive gear. look inside the main housing. if you see white plastic shavings that would confirm the gears are stripped.

kits are available for under $25.00. don't buy the one with just the gears, get the new shaft sprocket etc.

Not a difficult repair. However, be sure to follow the instructions carefully. the position of the chain & sprocket when you put it back together do matter.

Good Luck


Mar 02, 2015 | Sears Craftsman LiftMaster Chamberlain...

1 Answer

I can not get the chain to fit on the 3/4hp garage door opener I purchased form Sears

There is typically an adjustment on the chain that allows you to tighten the chain as it stretches with time.

The adjuster should look like a piece of threaded rod that is in-line with the chain. It should have a nut on it that takes a 7/16" or 1/2" open-end wrench to tighten or loosen the chain.

Sometimes, the adjustment mechanism comes from the factory in a state that makes the chain too tight. Try loosening the adjuster until the chain will fit and then make final adjustments.

Because thus is a chain with a sprocket at the motor end and another sprocket at the door end, sometimes more slack in the chain is required to get it seated properly in both sprockets. A helper may be required to help you get the chain in both sprockets simultaneously without too much slack in the chain between sprockets, but with just enough slack to prevent binding.

Another thing at which you should take a look, is the armature in which the chain rides. This is typically in 2 or more pieces in the box, requiring the installer to slip one inside the other. Ensure that the joints are fully engaged, which would make the length of chain required a bit shorter.

The last thing you want to inspect is that the chain in installed to the inside of any chain guards. These are present, typically along the longer spans on the sides of the long arm, to ensure that if a chain breaks or becomes bound and pops off a sprocket (think of popping a bicycle chain when you were a kid), it will not fall to the ground, or hit your car or a person. If you inadvertently routed the chain to the outside of one or more of these guards, your chain will certainly be too short.

I hope this helps!

Oct 14, 2014 | Building Materials

1 Answer

How do I put my chain back on a Stanley 8500 Garage door opener?

First you must make sure the sprocket on the garage door opener is spinning clockwise and reaches its limit and stops, you can easily put a pair of pliers between the #1 and #2 terminals on the garage door opener and start the sprocket spinning or just grab a remote and watch from the back of the unit (looking towards garage door ) and make sure it,s direction is clockwise, Once it stops you wanna loosen the chain enough so you can position the carriage which is connected to the chain and with your door closed send the carriage down far enough so that the carriage and the trolley both engage then all you have to do is put the chain over the sprocket and tighten up the tensioner that is located on the trolley...not to tight and not to loose is what you would want in an adjustment ! since you already ran the sprocket in the down position your door is now ready to test ...when you press your remote or wall station the door will travel up, You have to do it this way , if you don,t can damage the machine or your door ! Good luck and hope I was able to help you with your dilemma!

May 07, 2014 | Stanley Building Materials

1 Answer

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...

3 Answers

Liftmaster tries to close instead of open door

Remove the chain from the sprocket and then run the motor until the sprocket turns clockwise and stops. With the door in the closed position and everything attached to it, replace the chain and tighten. This will get everything back into sync. You will most likely have to tweak the up and down limits a bit. Do not over tighten the chain. It should sag just a little.

Oct 25, 2009 | Sears Craftsman LiftMaster Chamberlain...

1 Answer

Craftsman 1/2HP Door Opener won't stay closed

Loosen the chain and run the opener until the sprocket runs in the counter clockwise direction and stops. Now with the door in the open position replace the chain. This will get everything back into sync but I hope you remembered where all those controls were. You need to put them back in their original positions.

Jun 06, 2009 | Sears Craftsman LiftMaster Chamberlain...

1 Answer

Craftsman opener motor works, but chain does not move.

If the motor is working but the chain does not move you must remove the cover on the motor and check to see that the chain is on the sprocket. If the chain is on the sprocket and the sprocket is not moving but the motor shaft is moving then the sprocket must be retightened onto the motor shaft.

Apr 20, 2009 | Sears Craftsman LiftMaster Chamberlain...

2 Answers

Sears opener wont open or close more than 12 inches

You may have put the chain back on out of "sync" with in internal up and down stops. You may have to take the chain off the motor sprocket and run the motor to make sure it is stopped in the down position ( watch the rotation of the sprocket to determine up or down position) When the motor is stopped in the down position put the chain back on with the chain Carriage in the down position. Then you can fine tune the up and down stop positions with the adjustment screws on the side.

Feb 05, 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...

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