Replacing plastic gear in Lift Master


Old 03-12-10, 04:06 PM
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Gear replacement instructions scanned in, with pictures

Hi, I just replaced the gear in my Sears (Liftmaster), and made a webpage with photos and the written printed instruction sheets scanned in. Now you can read the instructions and decide if you want to do this yourself (it's not too hard really).

liftmaster repair instructions here

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Old 03-13-10, 09:26 PM
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For those that still have problems after replacing gear...

Thanks to all the previous posters. This really helped me save about $140.
After installing the new plastic gear, my trolley would only travel a few inches and reverse and then stop. No clicking, no light (bulbs) flashing. So after noticing an led flashing 5 times next to the red control button, I found what the error code meant.

# of flashes

1 The Protector System wire open or totally misaligned

2 The Protector System wire shorted or black/white wire reversal

3 Door Control or Multi-Function control Panel wire shorted

4 IR sensor slightly misaligned (dim or flashing sensor LED)

5 Motor overheated/Possible RPM sensor failure -- unplug to reset

6 Motor circuit failure -- replace RX/LX board

Rapid Flashing - Chamberlain transmitter with the correct format code being received
(opener not necessarily programmed to respond

I was hoping that the motor had not overheated or that I would have to purchase another RPM sensor, so I took a Q-tip and cleaned out between the sensor. That did the trick!!! Of course, this took me an hour or two to figure out but it is done.

Thanks again everyone!!!! Beer 4U2

Old 03-14-10, 10:43 AM
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Yup, gotta clean that little electric eye.

My instructions for this repair:

Clean here:

Old 02-01-11, 05:36 PM
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Cool PDF on how to Replace the gear...
Old 02-17-11, 06:34 PM
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Replaced mine today for like $26 from MINT now...Thanks!!!!
Old 03-05-11, 10:14 AM
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Maybe I can help

I am a garage door repair tech with 14 years experience. I have repaired this problem several times, almost every time it is caused by a problem with the door. Like a broken spring or something stopping or slowing the movement of the door. This gear is designed to fail before damaging something more expensive. The first thing to do before trying to run the door with a repaired or replaced opener, is to try to open an close the door several times by hand. The opener's job is only to replace you "moving" the door, the springs do the heavy lifting. If you can't open the door, neither can the opener. If you find a problem with the springs, cables, or anything connect to either of these, I suggest that you call a professional to help, you can severly get hurt by these systems if you do not know how to safely adjust them. I hope this has been helpful to some of you, Be careful PLEASE!
Old 09-22-11, 06:58 AM
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dual sprocket

Does anyone know if I can use the single sprocket style ( cheaper and more common) in place of a dual sprocket output shaft? I don't need two speeds but I do need a new output shaft cause the dual gears broke off the end of the shaft as well as the big plastic gear getting chewed up. I know I will loose the option of having two different speeds but is there a reason it can not be done?
Old 09-22-11, 01:37 PM
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No reason at all. That short sentence says it all but my response has to be 25 characters.
Old 12-29-11, 07:35 PM
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Awesome post, guys; a real lifesaver for me! I registered just to thank you all.

The actual parts replacement went fine, but i had the issue of the door moving just a few inches then the dreaded 5-flash LED. But it was also the simple solution - i did not have the motor shaft pushed all the way back when i tightened the collar after replacing the worm gear. (I had actually pushed the shaft the wrong way, so i had as much play as possible!)
Old 08-10-14, 02:01 PM
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I have an LiftMaster 1/3 HP opener that I replaced the main shaft, gear and worm gear. Did everything that the instructions said to do. However, when I press the button the gear starts and only goes about a couple of inches before the interrupter cup is pushed off. Any ideas??
Old 08-10-14, 09:06 PM
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Welcome to the forums.

Did you read the post directly above yours where he talks about the shaft play ??
Old 10-28-14, 03:39 PM
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My garage door opener has noise when door open/close. It looks like the noise comes from gear. So I replaced the kit (41C4220A Gear and Sprocket Assembly) and greased it following instructions here. I didn't replace the worm drive.
For first few door moves, the noise disappeared and the door open/close fine. But the noise comes out again after few opens/closes, Is there anything I missed? Any suggestion?
Old 04-03-15, 05:48 PM
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Liftmaster 1260 1/2 HP Shredded plastic gears

I read thoroughly through this thread and this is my conclusion to my situation.

Our garage door itself has been very rough closing (especially in the winter months) especially in the last leg of the door closing (the last panel of the garage door seems to have friction with the metal guides/frame of the door). It's an 18 year old door/opener.

Many times we had to 'fight' to get the door closed by stopping then restarting the door at the point it failed...that's the only way we could get it to close. The motor was fine (and still is) but it finally has chewed the gears.

Where I am in Canada, the cheapest gear assembly kit is $40 and I will need to have to hire someone to take a look at the friction on the door itself anyways + fix the opener (I don't think I'd have the patience to fix this!). This could take 1-3 hours of labour from a pro to open/fix the unit (with replacement parts), so my probable best scenario is to buy a new opener for about $200 and have the pro install it. A little bit more $$$ for the unit but less labour charges and I won't have to spend several days working on it.

Any thoughts?

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