Question about liftmaster Chamberlain Garage Door Opener Transmitter 300MC

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Garage door will not work

I have 1/2 hp chamberalin door opener. the worm gear and the other plastice grar wore out I replaced these 2 gears now my door open and close only 1 foot,

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  • jenandjeff3 Jan 17, 2009

    I Have the same problem, everything looks to be connected. my door only moves 6-8 inches and then goes in the opposite direction. Can somebody help this is so frustrating.


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Check to see if you plugged in the 4 wire limit assy. harness.

Posted on Jan 06, 2009

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1 Answer

Worm gear is good. drive gear is worn out

contact Chamberlain thru their website . perhaps they sell gears .

Sep 02, 2015 | liftmaster Chamberlain Garage Door Opener...

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.
You can buy a replacement gear kit from sears (call them first, with your model number, to make sure).
It'll take you about a half hour to fix it.

Apr 23, 2011 | liftmaster Chamberlain Garage Door Opener...

1 Answer

Liftmaster Formula One. Garage door will open and close, only if I give a little manual help, and even then the trolley runs very rough. When the door is disconnected from the trolley, the trolley and...

Sounds like the gears are stripped.

Open the housing and see if there are white plastic shavings inside.

If so

You can get a gear kit and fix it yourself $ 35 - $50

Or for around $ 125.00 get a pro to fix the problem and lube, adjust, service the door and opener.

You pretty much have to take the unit apart all the way - it's not a simple project but it is doable for a diyer with reasonable skills 1-2 hours.

Follow the instructions step by step and don't cheat by leaving the gear thats hard to get to. The wear pattern on it will chew up your new gear in a few months and you will be doing it all over again.

Hope this helps

Mar 17, 2011 | liftmaster Chamberlain Garage Door Opener...

1 Answer

I have a Liftmaster formula1 garage door operator, belt drive. It just ate the main plastic drive gear. This operator has been in operation for 15 years with no problems. Any ideas?



Unplug the unit - take of the cover - you will find white shavings inside - these confirm the Get the gear AND sprocket kit.


Oct 17, 2010 | liftmaster Chamberlain Garage Door Opener...

1 Answer

The motor makes a noise but seems locked up. 2265R Chamberlain lift master professional 1/2 hp

Make sure the door is running well with out the openers help first of all. If it is making this sound then look inside the unit with the unit unplugged for white shavings. If so you will need to replace the gears. Thanks BB

Mar 30, 2010 | liftmaster Chamberlain Garage Door Opener...

1 Answer

Liftmaster 1/2 HP Garage Door opener won't open or close. Has been working fine until I pulled out this morning. The door will move freely if I disengage from opener. Went up ladder to see chain not...

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.

Here is a link for a parts supplier. I don't know your model but it looks like most of the Liftmaster worm screw gears and drive gears are plastic so it's possible that one of them has cracked.

Feb 14, 2010 | liftmaster Chamberlain Garage Door Opener...

1 Answer

Gargae door sounds like it opens but nothing happens

if the door is not opening and you hear the motor turning you have shreded the gear inside the opener it's only made of plastic. you can check this by taking the cover off and you will see a bunch of white dust. gear gone you can replace this gear.

Mar 20, 2009 | liftmaster Chamberlain Garage Door Opener...

1 Answer

When i try to open the door it sounds stuck makin a wierd nosie

check to see if the springs above the door are broken of it's the gear inside the operator that has been shreded you can find that our buy taking the cover off and theres a bunch of **** plastic dust means your gear has gone. you can change this gear.

Mar 20, 2009 | liftmaster Chamberlain Garage Door Opener...

1 Answer

Lift-Master GDO goes up, not down

If the door operates freely without any binding, while operating it manually then It would appear that the obstruction sensor mounted across the doors path is ether out of alignment, lens dirty,or malfunctioning

Feb 21, 2009 | liftmaster Chamberlain Garage Door Opener...

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