Liftmaster/Chamberlain/Sentex 41A2817 Gear Kit

Great for my 1995 Chamberlain. Works great now! Highly recommend watching youtube videos to do this as included instructions are on a small piece of paper, printed at a fairly low resolution. This is a very doable project for the average DIYer. It's not easy, but it can be done. Here are a couple tips and a couple places I was hung up:--Take pics of wiring configurations--Don't mess with the travel/force settings and don't unwire the back where all the controller inputs connect if you don't have to.--You'll need a punch that's the exact width of the roll-pin that holds the white gear on the shaft. If it's not the same width, it'll widen the pin, which is counterproductive. They are a pain to get out. Strike hard and true and a lot.--Once you drop the motor assembly, you'll need to use a flat screwdriver and a hammer to get all the pieces off the shaft. There's one collar that really stuck for me and was the last piece preventing me from accessing the worm gear.--Related to the last part, get everything as far onto the shaft as you can once you put it all back together. I failed to do so on the first try and had to pull the motor back out to fix it. The problem that arises is that the shaft moves in and out and the slop makes it impossible for the RPM sensor to work right. This caused my door to open and close about 5' before reversing direction. Pulled it out, helped the parts down the motor shaft with a hammer, put it all back together and worked great.--The last fun part is putting the chain back on so that it's aligned properly upon open/close. During this phase of moving it and testing it, do NOT allow the door to hit the metal stops in the track when testing it out. All your tension will go to one side and the opener can't move it. If this happens, be aware that the tension releases with the fury of hell. i.e., stand on the opposite side so when it lets go it doesn't gash your face...or maybe have a pro handle it. I released it from the drive sprocket with a wrench and it made quite the noise.--If you pull this off, you'll become a garage door opener pro and get a really good understanding of how it works, which I have to say is really cool and why I do these projects myself. It'll take a good amount of time if you don't know what you're doing, so maybe clear your schedule for an afternoon. Good luck

Our house came with two older (early 2000s) Craftsman 1/2 hp openers. About six months after we moved in, one opener stopped working. The motor ran, but the door did not budge. I assumed it was the typical Chamberlain/LiftMaster/Craftsman nylon gear failure, and when I opened the unit, a mountain of white nylon shavings confirmed my suspicion.As most other reviewers have noted, this isn't the simplest job in the world, but it isn't brain surgery, either. With a little bit of patience and a few ordinary hand tools, you'll have your opener back in service in an hour or so.A few notes:- You don't need to remove the opener to replace the drive gear.- Be very careful removing the plastic E-clip and door position gear from the bottom of the shaft. The kit does not include replacements for these parts. The clip feels somewhat fragile.- Read the instructions carefully. Most importantly, start with the door closed and the opener stopped at the full-closed position. This will help enormously in re-timing the opener at the end of the job (which is a piece of cake).- The instructions suggest removing the motor first. I found this to be unnecessary. I was able to get a small ratchet and 5/16" socket on all three of the bolts that hold the driveshaft flange on to the top of the opener. This may save you a few minutes of work and some hassle, especially while working on a ladder. As the instructions note, the worm gear on the motor shaft typically doesn't need to be replaced because it isn't the weak link. Mine looked brand new.- You may end up with leftover parts. This is not a problem. The kit is designed to cover numerous models, and not every model uses the same pieces. I ended up using the drive gear, the c-clip, the driveshaft bushing, the wave washer, and the other two washers for the driveshaft. My bushing was very stiff, which I suspect was the reason for the nylon gear failure. I coated the driveshaft bearing surface and the inside of the new bushing with teflon and the assembly spun very freely.- The hardest part of the whole job is driving out the roll pins on either side of the gear. Driving them out isn't that hard, but keeping everything in place can be. I laid the driveshaft across two pieces of 2x4, with the gear in the gap between the 2x4s, and ran a drywall screw through the third, unused hole (you'll see what I'm talking about) in the driveshaft. This worked perfectly to hold the shaft steady and kept the roll pins vertical. Line up your punch, a few taps with the hammer, and you're all set. I used the new roll pins.- Timing the opener seems to be the most daunting step for some people. It's simple, though. There is a double-ended metal contact attached to a threaded shaft that spins perpendicular to the chain driveshaft. When it gets to one extent of its travel, it hits a metal contact that tells the control board the door is closed. When it gets to the opposite extent of its travel, it hits another metal contact that tells the control board the door is open. These two contacts are on threaded rods that are turned by the screws accessible through the opener case for upper and lower limit stops. So long as you start with the door closed, the chain trolley engaged, and the opener in the "fully closed" position (i.e., the double-ended metal contact is just barely touching the lower limit contact), you probably won't need to change a thing. If things are off kilter (i.e., if the opener stopped halfway up and you pulled the manual release and closed it), just get them back where they need to be. Close the door, slide the trolley and engage it with the door, THEN put the chain back on and set the chain tension. You may want to run the opener with the chain off to get it in the "fully closed" position. The instructions explain how to do this by watching the direction of the chain sprocket rotation to ascertain whether the opener is opening or closing. I didn't have a remote handy as I use Homelink, so I plugged the opener in, pressed the button on the wall, then pressed it again. If the opener just stopped, I knew it was moving in the up direction. If it reverses, you know it was moving in the down direction (and thus you then need to run the opener again after it stops to get back to fully closed). Unplug the opener, reinstall the chain, set the tension, and you should have very little work to do to set the up/down limits of travel.Congratulations, you just saved $200 and the hassle of installing a new opener! Make sure to lube the chain adequately, check the tension after opening and closing the door a few times, and watch for proper operation of your door rollers and springs in case a mechanical malfunction was to blame for your gear failure.

Shipping was faster than expected. I opened the cover on my opener before I ordered these parts and noticed the large gear (not the worm gear) was stripped. It was all dusty inside from the gear so I ordered this set instead of just the gear just in case I needed more parts when I took it apart.Turns out, I did NOT need the other parts- not even the cotter pins used to keep the gear in place- I just used the old ones again since they were fine after I took them out. At least I have the grease and another worm gear if I need it. Directions were clear and since I only needed to replace the large gear, it went pretty quick considering I didn't have to, nor wanted to, take the whole garage door opener off the ceiling (about 30 minutes). The longest part of it, was unscrewing the 3 screws underneath the top of the opener.I did manage to put a few small dents from my feet on the top of my car, so I guess I should have used a ladder.Works as good as new. Easy way to save some $$ when you don't need to get a whole new opener.