Liftmaster 1265 won't motor more than a foot in the down

If you buy the gear kit part number 41A2817 it comes with instructions. It is available at any good door opener service company.

The drive gear must be stripped.

Check your door springs and also remove the cover from the motor unit and check the drive gear. It is a white nylon gear just in front of the motor and may be stripped.

Check to make sure you don't have a broken door spring and also remove the cover from the motor unit and check the drive gear. It is a white nylon gear just in front of the motor and may be stripped.

Remove the cover from the motor unit and check the drive gear. It is white nylon and is just in front of the motor. Most likely stripped.

mtr dr gear stripped if you got a sears parts around your part # 41a2817 no grease on gears stripped gear do it your self, instructions in box, or best to pay someone that does it every day... less can of worms...

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.

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.

Open case, & see if white shavings from gear stripped out are laying on bottom of case.

I have a 1265 and took the cover off (unplug first).
There are screws securing the cover: 2 on each side at top, 2 at either end bottom.
Then I disconnected the chain.
There are 3 hex head screws securing the drive gear assembly (of course they thread from the inside out which makes taking them out a bit time consuming). Take care not to damage the circuit board or other electronic connections.
Then at the bottom of the shaft is the "limit switch assembly" that is clipped into the metal housing. Squeeze the 2 on the outside and it should swing free.
Then at the very end of the shaft there is another plastic gear. It is secured by a 3 prong plastic clip. Pull the outside clips away from the shaft while pushing the center piece back through the shaft. The gear should come off and you can now remove the gear and sprocket assembly up through the assembly.
call 800 528 2817 and order the "Gear and Sprocket Assembly".
I am waiting for the part and assume we reverse the order above to reinstall.