Hi,

I saw your post from last March about replacing the drive gear and worm gear on your garage door opener. I have the same problem. I have located the part, but before sending for it I wondered how difficult this is to do? Did anyone help you in your quest for assistance? I would be very grateful if you could let me have any pointers.

Thanks so much.

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.

* 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.

Good luck, if you have anymore questions you can post on here or email me at Billi_6@msn.com

Doorguy,
You are a real expert on these GDO.
Following your advice, I just ordered the nylon gear only on ebay for my unit ($18 shipped). It's supposed to come with grease and instructions. Can you tell me what grease is used in these plastic parts?
What is the life expectancy?
Thanks!

friendly jacek I can answer your questions. The grease that comes with the gear kit should be used on the teeth of the drive gear. That gear takes the full weight of the door when it is opening. As far as lift expectancy, that totally depends on the condition of your door hardware and springs. You should lift the door manually occasionally and if it is heavy to you it is heavy for that poor old gear. I always recommend a person has his wife lift the door. That answers the question of the door condition.

I've just finished replacing the drive gear and worm gear on a Sears/Craftsman garage door opener. Now when I activate the motor it runs for a few seconds, reverses and runs for a few more, then stops. I don't have the chain hooked up to it, so its got nothing to do with the door or chain. Is this fixable or is the fault with the circuit board?

It really helps when you start your own post rather than tacking onto someone another. It sure makes it easier for those who want to help you.

But did you remember to replace the black plastic interrupter cup on the end of the motor shaft?

Yes, I put the black plastic cap back on, and the four pin circuit board is plugged in. When experimenting with it I unplugged the 4 pin circuit board. It was exactly the same with it plugged in or unplugged.

When your replaced the worm gear you may have not pushed the shaft on the motor all the way back. Pull that black cup off the end of the shaft, loosen the coupler. Where the shaft pokes out the front of the motor, push it back as far as it will go. While holding the shaft tighten the coupler back up and put the black cup back on see if that does it.

It Works! That was it. I didn't have the coupler on far enough, so the vanes on the black cup were not between the sensors on the circuit board. Once I fixed that it was okay. Thank you very much for your help.

Doorguy06, great instructions on replacing the gear. Would it be prudent to replace the gear and sprocket assembly (41C4220A) rather than the just drive/worm gear kit(41A287)? Is it any easier? Thanks.

BUMP

Hi doorguy06,

Thanks for inspiring me to do it myself, it was a snap and saved me about $150 here in Folsom, CA. I ordered the gear from this ebay seller for $18.95 with free shipping and it came with grease.

Thanks a bunch.

Just a couple notes though.

1. If ordering only the gear be sure to save the removed lower roll pin (it's not necessary to remove the upper roll pin).

2. Also, that 5/16 socket will need to be a deep-well (preferably narrow shanked) and you'll also need an extension.

Hello all - new posting:
I recently replaced both garage door springs (one had broken). Then the Craftsman opener (6 or 7 yrs. old) would only operate for a few seconds, then reverse. Eventually, after my brother tinkered with it(don't know what he did), the motor would whir for a few seconds then reverse and stop - no chain movement. I opened the cover and found a few loose chips of the drive gear, and the drive gear had moved out of position and was jammed against the worm gear. I'm wondering: 1)which gear kit to get (with or without the shaft), and what caused the problem. 2)Maybe the springs are to stiff - as soon as the carriage is released from the opener, the door flies open. 3)Could these springs have required too much downforce for the motor to close the door and made the gear break. Need to address this quickly for my mother.
Any help appreciated.

Your first job is to have that door corrected. I would get a technician out before someone is hurt. If those springs are that mis-adjusted they may break.

don 1:
You don't think it could just be the wrong springs? The tension isn't too bad for me to work on them, with the door up. What about the gears?

The gear was probably worn in the first place and you did not know it. Running an opener up and down a few times even with the wrong spring is not going to wear out the gear that quick. I don't understand what you mean when you say the gear is out of place and jammed against the worm gear.

The drive gear meshes with the worm gear which is normal. If all you are seeing is shavings or broken pieces of the gear with no signs of ground up metal get the gear. If there are signs of ground up metal get the gear kit.

Check the balance of the door it should stay on the ground, stay half way up and stay all the way up if you let go of it. Even if you replace the gear, the spring tension needs to be corrected to give you more life out of your opener. I too would recommend calling someone out to take a look.

Yes it could be wrong springs. You are in a situation that can get dangerous fast. Get someone there that knows what they are doing.

doorguy06:

I recently replaced the Drive Gear for our Overhead GDO. It lasted for approximately three weeks then re-stripped. The worm gear appears fine and the bushing are okay. Also the balance seems okay. What could be causing this recurring problem?

No lubrication on gear. The gear kit comes with a tube of white grease. Use this heavily on gear. If the door is heavy when you lift it by hand it will cause this.

Hi, thanks for all the great instructions, I was able to remove all the parts, except the roll pin on the shaft. Is there any easier way to remove it?

If you leave the motor housing bolted up you can drive the roll pin out very easily. Sometimes I will use a pair of vice grips to hold the punch if it is a stubborn roll pin, but they always come out. Don't be afraid to give it a good smack with the hammer.

bump

Do you have to disconnect the chain to replace the gear?

Hi Doorguy06,

Thanks again for your instructions on how to replace the gear. I just replaced one; pretty simple and helpful instructions.

The door works fine now, except that when it's close, the door does not go all the way to ground. There is about one inch gap. Any idea or suggestion?

On the side of the motor unit you will find the 'down limit'. Turn this in the direction printed on the cover. One turn will probably do the trick. If you adjust this too far the door will hit the floor and reverse to the open position. A little tweaking will do the trick.

Thanks, Don. It did fix the problem.

Can anyone please tell me exactly how to get the drive gear off the shaft? Ours is stuck! We took out both roll pins. We have tried WD40 and tapping the gear all around with a hammer. Any other suggestions?
Thanks

Same as a previous problem on this forum, we installed a new plastice gear assembly when the old one was chewed up (why does this happen to begin with?). It worked 3 weeks, seemed to be getting louder and got chewed up again. Same symptoms, when opening the door (one large vs two small) it went up only one panel's worth and stopped, went down and never went back up again; making loud noise; gear is stripped again. We did not use "LOTS" of grease the first time around, but wonder if that is really all it takes? Should we buy another gear assembly and try again on a 10-yr old motor? (thereby spending $70 on an old unit vs $150 for a new one?)

We did a gear replacement as it was stripped - it lasted a couple days and then stripped again. I thought maybe the counter balance spring was not tight and the load on the motor excessive but after checking it, it seemed like maybe 10 pounds of upward pressure at most was needed to lift it. Any ideas as to what the issue is?

Compcoder,

It is a mechanically moving part that eventually wears out. Usually around the 8-10 year mark. Things such as improper door balance can help speed up the process. That sound like a problem you might have. Lift the door up manually if it is heavy for you to lift then it is heavy for the opener to lift. Openers aren't designed to bear the weight while lifting the door. The springs lift the door and the opener just guides it up. I would check to make sure your door is balanced and use all the grease that comes with the new gear.

jhfish,

Are you sure you used enough of the grease that came with the new gear?

doorguy06,
We did not get any grease with the new gear for the LiftMaster but added a little bit of silicone grease to it. Apparently not enough. Do you think that is the cause? Any other things come to mind? If not, I think we will replace the worm gear and the drive gear, grease the heck out of it and increase spring tension to lighten the load additionally.

jhfish,

Yes that is it. Dont worrr about replacing the worm gear. Just put another gear in and grease it up really good. It should come with grease if not contact who you bought if from and let them know.

The new bearing split while I was tapping it onto the motor shaft of my Craftsman garage door opener. I then tried the old bearing and it split too. After I buy a new shaft bearing kit, how can I avoid splitting the new bearing? Should I heat it up? Grind down the diameter of the shaft? I would appreciate your advice.

What bearing? Post the model number of your opener.

just the plastic gear/not the one on the motor shaft

1. disconnect power. and remove chain from sprocket(chain needs to be loosened and remember to tape the chain to the trolley) and then remove cover.

2) 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.

3. remove the 3 screws holding the shaft. they are at the top and attach to the frame of the box,

4. slide the shaft up and out of the hole.

5. remove the two roll pins that hold the gear on the shaft.

6. put new shaft on, replace the pins , grease up the sprocket and put back in unit.

7. screw the shaft back in place. reattach limit switches, connect chain on to sprocket. tighten chain.

8. connect power and adjust as required.

Hey home owners. Hire a Pro. We make it sound easy because we've done it a hundred times and we have all the right tools. There are a lot a variables that cause the gears to wear out. If you hire a pro they can fix the opener and make sure everything else is working properly so you get the longest life out of your new gear. Homeowners are always having problems with the openers after they try to fix them because the main gear drive may just be a symtom of a problem and not the main problem. A lot of times a mom and pop type door guy is you best bet because they deal with service more, not just new construction so they see these problems every day. Know you limits when it comes to DIY.

I think he split the little bearings (like thin washers) that slide on the shaft with the worm gear. I had to file a few rough spots on the motor shaft before mine would slide on without binding.
I scanned in the actual printed instruction sheet for this repair, and put in my own pictures here:
http://dl.dropbox.com/u/1347192/lifter/liftmaster_repair.html

Here is a link that might be useful: Liftmaster / Sears gear replacement instructions with pictures

Hello,

Thanks so much for these excellent instructions as well as the detailed pictures from "don2737".

I was able to complete this fairly easily. But, I wonder if I did something wrong.

The motor continously hums very quietly and remains quite hot. It is not actually trying to open or close the door, but more like power is going to it making it "ready".

If I unplug it for 10+ miunutes, then replug it in, it stops and is perfectly quiet, but the hum restarts after about 15 minutes.

It's a Sears Craftsman 1/2hp Part no. 41a5021-3b

Any ideas?

Thanks again.
BOB

I would like to thank all the folks here with your suggestions. I would especially like to thank Selvan777, as I followed his advice when changing the Drive Gear only. Yes, I only had to remove the lower roll pin, and funny that the roll pins that I received in the Sears kit were too small. It's working perfect again.

Only tricky part was getting the shaft back down so the gears meshed together. I had to pull the shaft back towards me by hand, wearing gloves, with some pressure and then it slipped right down. Applied grease completely on the new drive gear.

Thanks again to everyone on this forum. I'm sure I saved at least $150 and it's working as good as new. Sidebar, I did replace the rollers on the guide bars on both sides. I am a happy camper today.

Re: Challenger 9000M roll up door - 8 Foot tall & double door width. Replaced the opener gear and sprocket with new bushing. Didn't work right & found chain way too loose and plastic opener stop limits laying in tray. What is proper chain tension and where do stops go?

My advice is to call a professional. This is a black hole to a rabbit hole to a lost vortex to nowhere.

And extremely dangerous to boot.

Think about the strength of the coils and tension to move that door up and down...just think about it.

Updated instructions, large close up pics, on how to replace the gear:
http://www.dwdav.com/lifter/lift2014.html

Here is a link that might be useful: sears garage door opener gear repair replace

Should the small limit gears be greased?

Sorry not the actual limit gear but the small gear at the bottom of the shaft that has the plastic clip

My garage door opener (1/2 HP craftsman model #13953600) has grinding noise when door open/close. I followed the instructions here and replace the main gear including shaft (41C4220A), I didn't replace the worm gear. On first few moves, the door opens/closes fine without any noise, but the noise comes out again afterwards.

I don't know what it is. Worm gear looks ok. However, when I pushed motor shaft, it can move back and forth a little bit. I also can turn the "O" ring manually (on the shaft with worm gear). Is it normal? Is it because the worm gear gets loose?