Replacement for Liftmaster 41C4220A Gear and Sprocket Kit fits Chamberlain, Sears, Craftsman 1/3 and 1/2 HP Chain Drive Models

The product itself was great, but there are some ways to go wrong that aren't covered in most instructional videos. The installation on my Chamberlain 1255LM was fairly straightforward except for the one screw that you can't get a straight shot at. The best tool for that screw is a 1/4" ratchet. You need to watch at least one video so you can see how to pull the little tab at the bottom that holds the lower gear on. Tip 1: Before you do anything, check the balance of the door. When it's disconnected, you should be able to lift it about halfway and have is stay there when you let go of it (catch it if it drops, or you might break a window). If it's not balanced, the tension on the springs need adjustment. This is not too difficult, but it's fairly dangerous, especially if your springs are old, so you might want to bring in a pro. I did mine after watching a video. I bought two 2-foot pieces of rebar and ground down the ends on a bench grinder, just enough so that they fit snugly in the holes of the adjusting clamp. For safety, they need to go in all the way and you should never be in front of them or the spring when making the adjustment. Tip2: At the motor end, put a mark the angle iron and the chain, so you can put the chain back where it was. I don't know what to use for the mark. I used a yellow grease pencil and a piece of blue painters tape, but by the time I got the chain on, the tape had moved and the mark on the chain was gone. It might have worked better if I put a mark at both ends. I was close, but had to do a little adjusting of the Up and Down screws on the side of the unit. Tip 3: When you take the chain off. Hook it on the motor end of the angle iron that runs from the motor to the beam over the door. Tip 3: The the bottom gear of the kit meshes with a small gear to the right of it. That gear tells the system where to stop based on the two up and down adjusting screws on the side of the unit. If there's a gap between the two gears, the motor won't know when to stop. The gap is there because the black plastic housing for the gear on the right has come loose. It snaps in. Make sure it's tight and the gears are in contact with each other. Tip 4: This is the big one. When your gear stripped. The door was likely either all the way up or all the way down. The control unit may be confused about which one it is. On mine, when I reconnected the chain, the door came up and jammed into the stop bolt near the motor. The control unit thought the door was down, so when I pressed the button the door tried to continue going up, then either clicked, hummed, or did nothing (because it was overheated). Here's how to avoid that. While the chain is off. Run the door (it won't move because the chain is off). Watch the big white gear (the one that stripped). Look at the gear from below. When it stops, you can press the button again and it will reverse direction. When it's rotating counter-clockwise, it thinks the door is going down. Clockwise, it thinks the door is going up. Look where the trolley is (the thing on the chain that connects to the bracket on the door). If the trolley is near the motor, make the gear go counter-clockwise until it stops. Then lift up the door until it snaps into the trolley. If it's at the far end, away from the motor. Do the opposite. Make the gear rotate clockwise until it stops. Then move the door until it snaps in. Then put the chain back on. Tighten it so that the middle of the chain is about 1/2" above the angle iron. It was likely too loose, which is what made the gear strip. Get the lock nut as tight as you can. If the chain not exactly where it was before you took it off, you may have to adjust the up and down screws on the side of the unit. The arrows show which way to turn the screw for more or less travel. Adjust the up screw until the door stops about 4-6" from the stop bolt. Then adjust the down screw until the door just hits the floor.

An exact fit and works well. This kit isn't available from the garage door opener manufacturer anymore.

Showed up on time and worked great

The gears went in with no problem. My top gear broke off and I had a hard time adjusting the stops because the chain was off totally. I had to call a garage door service to get it adjusted correctly. 129.00 later everything is ok.

My repair required that I needed only to replace the top sprocket gear - that had sheered off over the years. This kit has the complete assembly of parts needed for that: The new sprocket gear already mounted on the steel the shaft, with the plastic drive gear installed - plus the smaller lower gear (that is removed and re-installed during the overall installation). Also included are the grease, (crucial and correct for the job) and the complete HD worm drive gear - which I can’t imagine ever being damaged. (It is just so thick and heavy). Also - the bearings, clips, & support washers for that are in the bag as well. This is a super nice kit. Like most lift motor units that liftmaster/Chamberlain make - the replacement parts are very well supported - and seem to be commonly available at reasonable pricing. I always buy 2 kits of whatever I need. But I have 2 garage doors (and therefore, 2 units to maintain). Liftmaster made the units for Craftsman and others too. So the universal parts support is unrivaled. Whether you DIY or contract the repair - the pricing of these parts makes it hard to pass up. Highly recommended. A

Replace them all the time and these seem to be as good as original parts. Would recommend for sure

Great product, excellent value, easy to install

Used this kit on a Craftsman 1/2 HP opener circa 2003. Did not need the worm gears since the only issue was the top sprocket had sheared off. On the plus side, the kit appeared to contain all the necessary parts. They provided a good quantity of grease which was much appreciated. The only negative was the enclosed business card which referenced a website/qr code to their installation videos. It did go to their website, but the only videos I could find were for remote controls/mirrors. There are plenty of YT videos that will show how to do this install. The biggest takeaways: 1. It will be much easier to get the top plate and shaft off If you have a ratchet wrench or a very small quarter inch socket. One screw is near the center with no direct access from the bottom of the unit. A regular wrench will work, but will take forever. 2. The holes in the new top plate are not threaded by design. Use the existing screws to thread it from the bottom side PRIOR to installing. You will thank me later. 3. Getting the chain reattached can be a bit of a challenge. I used 3 spring clamps along the rod to limit chain sag. 4. When reattaching the chain, I used a couple of zip ties going through the chain and around the tab on the carrier. When you only have one set of hands, you can tighten the zip ties with needlenose pliers and get the bolt through the carrier far enough to get the nut threaded.