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The plastic gear in my CRAFTSMAN 139.53973SRT garage door opener needs to be replaced.

I can buy the replacement part without any problem.

But since this is the first time I am doing this, my questions are:

  1. Is it possible to replace this gear without unmounting the garage door opener?
  2. If this isn't possible, how do I unmount the garage door opener with minimum effort and time investment?
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1 Answer

up vote 3 down vote accepted

I found the answer at http://www.thathomesite.com/forums/load/garages/msg0321575526348.html?38 - here it is:

First off you don't have to replace the worm gear. Second, you need to make sure that the bushings in the gear kit are not worn. You can tell by looking and the very top of the unit, you will see ground up metal, or on the top of your drive gear will have a bunch of ground up metal. If this is the case you will need to get a 41C4220A which is the complete gear kit.

Otherwise replacing the gear is a cinch.

  1. Unplug the opener and pull the cover off.
  2. You will see two roll pins in the shaft that the gear slides onto. Position the gear so that you can use a 5/32nd punch to drive out the bottom roll pin. Your gear maybe worn enough that you can grab it by hand and position it, or you may have to hit the opener button and stop it so that it is in position.
  3. At the bottom of that shaft you have a smaller gear that drives the limit assembly. Pull the triton shaped keeper out and slide it off the shaft.
  4. Remove the limit switches. They snap into the bottom of the motor housing. You remove them by lightly squeezing them together on the end closest the gear you just removed. Leave all the wires connected to the limit switches. Unplug the RPM Sensor. It is located to the left of that big black cup on the back of the motor shaft, it has a four pin connector.
  5. On the left and right side of the motor housing you will see four black bolts holding the motor housing up. Use a 5/16th socket and remove all four of them.
  6. Slide the motor housing off the shaft (you can let the motor hang) and then the gear slides off.
  7. Lube up the new gear with the grease in the box and reverse the above procedure.
  8. MAKE SURE YOU HAVE THE BLACK CUP ON THE BACK OF THE MOTOR SHAFT PRESSED ALL THE WAY ON AND THAT THE FOUR PIN CIRCUIT BOARD NEXT TO IT IS PLUGGED IN, OTHERWISE IT WON'T WORK PROPERLY.*

Check the bushing in the motor housing that the gear shaft slides through, sometimes this has to be replaced but, very rarely in my experiences.

Don't worry about using anything else in that box.

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