The worm gear turns the (large white) drive gear. If the drive gear is stripped the worm gear cannot turn it.

According to another post in this section, the white gear is what turns the worm gear. A worm gear is sort of long, like a shaft, with spiral gear teeth on it. The gear that turns it, or is turned by it, is round and flat, with the teeth around the outer edge! If either gear has broken or chipped, or worn teeth, that may be the problem. If you aren't fully adept at repairing things, or not mechanically inclined, it would better to have Sears Service look at it!
Check the other posts in this section about Craftsman GDO's.(garage door openers) Several knowledgable folk have gone into this problem quite fully!
And then, if all else fails, try my method of fixing balky garage doors! Rustyj

Rusty you have it backwards. The worm gear turns the drive gear. It would be almost impossible the other way around. Maybe the confusing part is the name "drive gear". The worm gear is on the motor shaft so if the drive gear was turning it - well think about it.

help please. Installed the gear kit last night and now the door opens about 6 inches reverses for about 6 inches then stops. plus when the door is in the closed position, the opener is pushing the door down instead of pulling it up (door position and opener aren't in sync). any thoughts?

Loosen the chain at the trolley and remove it from the small sprocket on top of the motor unit. Run the unit until the sprocket has turned counterclockwise and stopped. This is the open door position for the motor unit. With the door in the open position replace the chain and tighten. You may have to make minor adjustments to the up and down limits on the side of the motor unit. Do not over tighten the chain. It should sag a little when the door is closed. If it is overtightened you will hear a clicking noise when it is moving.

GDO Guru's

My 1/2HP Craftsman GDO broke at the gear connecting to the Chain. The motor is still moving good.
Question:
1>What is the part number of the replacement part.
2>If I dismount the GDO from the center track and mounting brackets, can I still use the garage door manually? I need to take it off the mounting bracket and the track in order to replace the gear assembly ... I think.
3> Any advise to reconnect the chain back after replacing the gear assembly?

Your help is much appreciated.
axw

The part number for the gear & sprocket is 41C4220A. You can use the door manually by pulling down on the rope with the red handle. You do not need to take it off the mounting bracket or track to replace the gear assembly. Just follow these instructions to replace the gear and then to reconnect the chain. If you have any problems just post back and we will help.

Loosen the chain at the trolley and remove it from the small sprocket on top of the motor unit. Run the unit until the sprocket has turned counterclockwise and stopped. This is the open door position for the motor unit. With the door in the open position replace the chain and tighten. You may have to make minor adjustments to the up and down limits on the side of the motor unit. Do not over tighten the chain. It should sag a little when the door is closed. If it is overtightened you will hear a clicking noise when it is moving.

I may have misunderstood your post. If all you need is the white nylon gear, the part number is 41A2817.

Thanks Don,

I believe I will need to replace the entire gear assembly.
(41C4220A) The top part of the metal gear has snapped off the shaft. I believe I can buy the entire assembly on ebay : ($29)

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=6023370173&rd=1&sspagename=STRK%3AMEWA%3AIT&rd=1

Is this the correct part????

If I do not need to dismount the entire opener, do I have to unscrew the top 3 screws that holds the assembly?

How does the gear assembly fit in to the motor. Is it easy to replace ? I am afraid that I do not have much room on top to refit the unit with the new gear assembly, but I'll try.

In addition to the information above, I'd first find out why the gears broke in the first place. Most likely, your garage door springs need to be adjusted and/or the track and rollers need to be adjusted/lubed as well. The springs do most of the lifting. You should be able to open your garage door quite easily if you disengage the door opener. If you can't, that's your primary problem.

If you don't find the cause of the breakage, you might be replacing those gears quite often.

I'd leave the spring adjustments to a professional or you could end up with a severe injury.

Machiem, great questions

Yes I can life the GD. without any problem, although the track can use some grease. I plan to grease it to help the lifting. I do not intend to touch the spring for safty reasons. I have not use the GDO for 3 weeks over the holiday and when I came back to use it, I thnk the chain caught the top matel gear (sprocket) and snapped it from the shaft.
In addition, I have only 6-7 inches clearence to to top of the roof, I may have to dismount the GDO. prior to the replacement of the gear assembly.

Don't grease the track. The rollers are designed to roll in those tracks. The grease will only make it harder for the GDO to operate in cold weather.

Just a thank you note for everyone to provide their pointers, suggetsions, comments. I replaced the entire gear assembly on my GDO. It took me about 2 hours with the help of my wife. It works very good now.
It probably saved us hundreds of $$.
Kudo's to you all.
Regards
axw

I'm having the same issue. The drive gear is worn to the point that the worm gear won't turn it. The drive gear does not look especially easy to replace. Any tips on how to do this?

I understand the drive gear now comes with instructions.

Don is correct, the gear assembly comes with clear instructions and 2 sets of gear for 2 different model of GDO and gear assembly.

My GDO gear connected to the chain was practically destroyed from poor tension. How easy it is to repair?
I have not touched a GDO ever in my life until now. I follow the instructions that came with the spocket set.

0gt; unplug all electrical to the GDO
1> removed the GDO cover while it is still mounted on the ceiling.
2> removed the gear asembly and motor(a dozen of screws). REMEMBER TO LABEL ALL WIRES before you dissassemble the gear sets and motor.
3> Follow the instructions to install the right configuration for your GDO. Grease all washers and gears as you assemble it.
4> Mount the unit back on the GDO casing still on the ceiling. Reconnect all wires.
5> the instruction will tell you to power up the GDO and turn the gear to an open or close position (clockwise)
4> Grease and reattached the chain with tension adjustment.
5> Make sure you put the release back on before attaching the chain back to the GDO. Don't adjust the chain too tight or too lose (feel tension with your fingers)
6> adjust the sensor screws on the side to insure GDO stop at the proper place.
7> once you have everything adjusted, open and close it a few times and observe the chain movements. Grease the chain and gear contact.
8> if the wires are reconnected properly. The light should come on on openning and closing.
9> re-assemble the casing and off you go. You've just saved yourself $250 and learn a new trade;-)

Sounds complicated than it takes. It is worth a try.
I may still have the instruction sheet with me. If you need to see it, send me you address and I'll mail it to you. That is the least I can contribute to this useful forum.

Follow the link I posted earlier to purchase the gear assembly.

axw

axwaxw, your directions are great except: Please do not grease the chain. The chain doesn't need grease. It is not like your bicycle or motorcycle chain. It is indoors all its life.

Try loosening the chain until you can remove it from the small sprocket on the motor unit. Then run the motor until that small sprocket has turned counterclockwise until it stops. Then with the door in the open position replace the chain and tighten. Don't over tighten the chain. It should droop a little when the door is closed. This should get everything back where it belongs.

I have followed the above directions and replaced the gears. The problem I am having is my GDO motor will run for about 3 seconds then reverse direction. I do not have the chain attached. I was thinking maybe the sensor was causing the motor to reverse, but the GDO light doe not flash, so I do not think it is the sensor.

Could anybody advise what might be wrong with my GDO?

Thanks

Did you remember to replace the black plastic interruptor cup on the shaft of the motor? Make sure the quick disconnect is plugged in on the small P.C. board there also.

The interruptor cup is on and the quick disconnect is plugged in. If I hit the GDO button when the motor reverses, it will run for 3 seconds & then reverse. If I keep doing this I can get the motor to the closed position. Then when I hit the button it will run the open cycle all the way.

So this is only happening when trying to close.

Check the interrupter cup to see if it is pushed in all the way. If it is, check to see if the wires are connected to the RPM sensor, if the wiring is ok the RPM sensor is bad.

http://liftmaster.com/pdfdocs/A2217M.PDFif PG 38

I have a 1/2 HP 139.53975SRT, purchased in 2001 (6 years old) but just installed it for the first time this past weekend. When I press the remote button the opener makes a "clicking" noise and the gears do not move. I removed the cover, and both gears seem fine. I've removed the chain so there should be nothing externally preventing the gears from moving. I haven't attached the sensors on either side of the door yet, would not having the sensors installed prevent the opener from working.

Thanks for any help you can provide!

Not having the sensors connected will not prevent the opener from starting to run. I would advise you to get the owners manual out and start at step #1 and make sure you did not skip something. The first time you tried the opener did it run or did it just click?

Hi, I purchased a home about 8 months ago and it had a Craftsman 139.53975SRT installed. It worked fine until yesterday when the spring broke. I went to Lowes and the attendant told me that I would need two springs and that they would need to be installed on the sides(ceiling) along side the tracks for the door. Currently I only have 1 spring and it is located on the wall directly above the framing for my garage door. If anybody has the part number of the spring or any information I would appreciate the help.

I have an old Craftsman GDO that has the same problem as previously described by axwaxw in this thread. Basically it just needs a new white nylon gear. Before I buy a new one I just want to make sure I can get the old one off the shaft without causing more damage. It looks like I need to remove one or two round steel pins. Can someone tell me the best way to do that? Is a special tool required?

You will need a punch slightly smaller than the diameter of the pin. You can also grind off the point of a proper sized nail and use it.

I believe this was asked above...but want to make sure its the same problem. I recently replaced the drive and worm gears in my opener. Got everything re-assembled....correctly I believe. However, when i try to open the door it goes up 6-8 inches, back down, and then back up the 6-8 inches...where it stops. I tried messing with the limits and forces, but not thinking that was the fix. Something was said about removing the chain from the top sprocket and cycling the opener??

I have a craftsman 1/2 hp. I just put the chain back on the sprocket and tightened it. With the door in closed position it wants to continue closing after pressing button on the remote. It doesnt want to open. If I open the door by hand then hit button it should close. will this cause it to self adjust, if not how can i correct it.

I answered my question. Took chain off sprocket, made it run once, after it stopped reapplied chain works normal.

this forum is great. i got the drive gear and worm gear (part no. 41C4220A) from ebay and replaced it last month. The instructions were pretty informative. Now i found that the gear has worn out again and when i open the cover i saw a lot of plastic shavings. When the opener is disengaged i could manually lift the door without any extra effort ( infact i let my 8 yr old try it and she could lift it. what could be other reasons for the gear to worn out so quickly. thx

Hello everyone,
I am helping a spouse of a deployed troop. She asked me to look at her garage door. It looked/sounded like a similar problem I had 1+ years ago. Took cover off and sure enough, plastic gear was worn to the bone. Having paid a few hundred dollars for a repair that seemed quite simple I told her I would tackle the job. I've read several forums including this one and found out what I needed to do. I ordered the assembly kit(41A2817) on ebay for $21.95. after placing the order and more research I am concerned that the cause of this worn gear is from the doors difficulty in opening. The top gear holding the chain has no shavings or worn and everything otherwise seems to be in good working order. I feel this is the least I can do for one of our troops deployed and already dealing with a great deal of stress and hardship. However, I do not want to tackle this job if it is going to be too difficult or may have to be redone in a month or so due to stress on the gears as a result of a problem with the door.Any advise/assistance would be greatly appreciated.

Does anyone know where I can score an owner's manual for a Craftsman 139.53975srt GDO, without having to pony up $5 at sears.com?

Even a PDF somewhere would be great!

Thanks,
Steve

Hello.
I have just moved into a house built in '95. not sure how old that makes the Sears Craftsman 1/2 HP garage door opener, but i am online searching to find a fix. I know nothing about GDO's. there is a green light blinking on it, and if i press the button in the garage, or on either of the remotes, i hear a humming noise for a few seconds, and thats it. i have noticed there are these 2 sensors you guys talk about by the door. Any ideas from anyone on where to start? Or should i be calling a repairman?
thanx!

My chain has gone up and will not come down now. The sensors are working and the area is clear. The lights are steady and do not blink. When the button is hit, it seems like it is trying to go up more, but it's already at the top. After a couple of seconds it stops trying to go up. Is there a way to get the chain to release so it will come down and then it can attach to the door and pull it up?
Thanks.

I have a challenger 1/3 hp opener, 16 yrs old. Teeth are worn off gear drive which the chain rides on. I can get the gear locally, but how do I remove the motor shaft to get in to replace the gear? Looks like a rivet holding the assembly together. Any thoughts? Thanks!

Rob

My thanks go out to all who have posted to this forum. I am a 50 year young, single female, who experienced the "motor whirring - no door open" problem. Due to the detailed comments left here, I had the confidence to order and successfully replace the gear drive on my Craftsman GDO. I feel great!! Thanks to all, especially Don, when my door only opened a few inches. :) :)

RE - INTERRUPTER CUP. I found out that the re-assembly of the hard plastic worm gear on the motor shaft and the bushings after that is really important - get everything as tight towards the motor as possible. I bought the replacement gear kit ($32 Canadian) and put it all back together. When I tried it out without the chain attached, it was 2 seconds one direction, 2 seconds in reverse and nothing else. I thought I had messed up a circuit board and even bought a new Sears GDO for $210 (CDN). One last try at troubleshooting with my son. It turns out that there is a tiny light beam on the 1" x 1" circuit board at the end of the shaft. The vanes on the Interrupter Cup have to break this beam for the GDO to function properly. But because the shaft was out to far, even though the Interrupter Cup was tight, it wasn't in far enough to break the beam. When I took it apart and moved the shaft in properly, the GDO worked properly. Took the new GDO back and saved $210 (plus the gear kit cost which would have been wasted).

Why does Sears always have their GDOs on sale? Why do they charge $49 / $59 for an extra remote or keyless remote entry pad? I guess because they can!

Okay. I replaced the drive gear today with no problems. The door opened with no problems, but now won't close more than about six inches. I've disengaged the door and even removed the chain, but it still won't move but about six inches downward and then moved back up. Any suggestions?

Is the light fixture on the opener flashing when it refuses to go up? If so, your sensors are not aligned or disconnected. See the instruction sheets at the bottom of the instruction page I made:
http://dl.dropbox.com/u/1347192/lifter/liftmaster_repair.html

Here is a link that might be useful: Sears craftsman garage door opener repair

I just had the same exact problem as kurtzj. I installed a new gear on the drive shaft and after that, the motor would only run a few seconds in either direction. I found an old post from sage66 that described the problem and actually contained a few photos that really helped. There is a small green led on the motor housing control panel that was blinking 5 times constantly. Apparently, this is an error code that says the door sensors are not aligned, or the rpm sensor is bad. The rpm sensor is a small circuit board with 4 wires next to the limit switches. There is a round black cap on the end of the drive shaft that has slots on the side, called the interruptor cap. This spins with the motor and the slots pass through the rpm sensor, which has an infrared sensor that it passes between. If the drive shaft has play that allows it to slide forward, the motor will shut down after a few seconds when the interruptor cap jumps out from between the sensors. What you need to do is take off the interruptor cap, and loosen the 2 allen screws that secure the thick brass ring and lock it to the shaft. Move it away from the motor enough to get a screwdriver blade between it and the washer behind it. Lock it down there and use a screwdriver to pull the shaft forward away from the motor all the way out. Loosen the 2 screws again and slide the locking ring all the way back to the washer without moving the shaft. Tighten the 2 screws and put the interruptor cap back on. This prevents it from jumping out from between the rpm sensor. After i did this, it worked fine.

I hope this helps someone else, because I never would have figured that out without help from sage66. The internet is great!

Good luck!

This is Fred777,my problem is that my garage door remotes work well from inside the house,with the garage door closed, I go outside to try to open the garage door but the garage door does not open at all. Can anyone please help me with this situation. Than you for your help Fred777