Craftsman Drive Gear Replacement Instructions

So you have a worn out drive gear in your opener and are contemplating on doing it yourself? No sweat. Follow these simple instructions and it shouldn’t take no more than an afternoon for the average jo.

The tools required to complete this project are as follows:

Either a Cordless Impact or good old fashion ratchet wrench.

1/4 inch socket

5/16 inch socket

1-2 inch extension

5/32 inch punch

1/2 inch open end wrench

1 pair of vice grips or c-clamp or equivalent

Step Ladder and a Hammer

*NOTE* All of the above tools may or may not be necessary depending on whether you’re replacing just the drive gear or whole gear and sprocket assembly. It’s a good idea to have them all on hand to be safe. My instructions below vary slightly from the manufactures instructions. My instructions are for the do it yourselfers and are almost verbatim on how I change every gear or gear and sprocket assembly. I have included some extra steps to make it a bit easier for the average jo. I give a lifetime warranty on my labor, so I am confident that following these instructions properly will not fail you because performing this job as stated hasn’t failed me. However, if you have any doubts please refer to the manufactures guide lines or have a professional in your area perform the task.

*When I refer to the Right and Left Side it is always done as if I am standing in the garage facing the door.*

First lets figure out if you need to replace just the drive gear or entire gear and sprocket assembly. Unplug the opener or disconnect its power source at the fuse panel if it is hardwired. Ensure the power is disconnected by trying to operate it via your wireless remote and or wall button. Next we’ll remove the cover of the opener.

If you’re standing underneath the opener facing the garage door, on the left and right sides of the opener, use the 1/4 inch socket to remove 2 screws on each side. Next, using the 1/4 inch socket remove the screws on the front and the back of the opener securing the plastic covers at the bottom. Depending on what model you have you will have either one or two screws. If you have only 1 screw you may need to utilize a screw driver to remove the screw.

Once you have the cover off inspect the drive gear. A worn drive gear will have white shavings evident when you remove the cover. You will need to inspect to make sure the bushing aren’t worn as well. Normally on the top of the drive gear you will find ground up metal. You may also see ground up metal on top of the opener where the chain or belt is attached to the sprocket. In some instances the sprocket may have broke off and the chain or belt is completely off. Another sign you may need to replace the whole gear and sprocket assembly is excess slack in the chain or belt without explanation. (I.E. it was never that loose before).

Now we know whether we need a drive gear or whole gear and sprocket assembly. So now we need to order the part or verify we have the correct part. The following part number is for chain drive gear and sprocket assembly’s only and should be part# 41C4220A. Just the drive gear kit should be part# 41A2817 and will work with both chain and belt driven openers. There are two belt drive gear and sprocket assembly’s. Please contact your manufacture with your opener model number to obtain the correct one. Otherwise perform a simple Google search on the listed part numbers to find the best price.

A common question is…..Why not just buy the plastic gear without the kit? I recommend the kit because you will also receive the grease to lubricate the gear as well as a bushing that I always replace in the motor housing mount. You will also receive the manufactures replacement instructions should you want to follow them instead of the one’s outlined.

Ok, now the fun begins!

#1 Start by vice gripping or clamping the rail in the front or rear of the trolley making sure you’re touching the trolley. You can also use a colored crayon or any other means of making a mark. The trolley is the piece that slides back and forth on your opener rail. You will see that the chain or belt attaches to the trolley on the left side in two places. You may have a cable connected to the front side (door side) and a chain connected on the back side (opener side) depending on make and model. Doing this will give you a reference point to reset the trolley in case it moves. This will ensure you will not throw the limits (how far up and down the opener moves the door) way off when reconnecting it.

*NOTE* If you’re replacing the Gear and Sprocket assembly, remove the chain or belt at this point. you do so by losing up the nut(s) on the trolley until you can pull the chain or belt off the sprocket.

#2 Remove the triton shaped keeper on the bottom of the shaft, underneath the smallest gear on the shaft, then remove the small gear.

#3 Remove the limit assembly. You do so by gently squeezing the front of it together nearest the point where you just removed the small gear and gently pull down. (I.E. the side that has the gear that meshes with the small gear you just removed)

*NOTE* If your only replacing the gear follow this next step otherwise skip to step #5.

#4 Using the 5/32 punch, remove the lower roll pin from the shaft. You may need to grab hold of the gear and move it manually to get it into a good position to drive the roll pin out. Some roll pins are stubborn. Don’t be afraid to give it a good smack with a hammer. You might want to use a pair of vice grips to hold the punch as I do sometimes. Once the roll pin is removed, save it.

#5 Remove the 4 pin wire connector next to the big black circle on the back of the motor shaft (RPM Sensor). Using your 5/16 socket with your ratchet or impact remove the 4 bolts holding the motor up. This is wear the extension will come in handy. Once the motor is free, slide the housing off the shaft. You can let it hank in the air by the wires. It won’t hurt anything.

*NOTE* If your only replacing the gear continue on to step #6. If you’re replacing the whole gear and sprocket assembly go to step #6(a).

#6 Remove the plastic gear by sliding it down the shaft. Some might need a little smack with a hammer to remove.

#6(a) Remove the 3 bolts holding the gear in place with your 5/16 inch socket. Remove the gear and sprocket through the top of the opener. Place the new gear and sprocket in the opener. Line up the three holes at the top and insert bolts. You’ll notice the bolt holes are not threaded. When you install the bolts they will thread themselves.

#7 Use the lubrication provided and lube the new gear, making sure you get the grease in between all the teeth on the gear and slide back on. Don’t use the grease sparingly. Lather the gear up.

#8 Remove the bushing the motor housing. The bushing I am referring to is circular in shape and a darker gray. It is the bushing that the bottom of the gear shaft slides through. You remove it by holding the motor housing and hitting the back of it with a hammer driving it out. In the kit find the similar bushing and put it back in by pressing it in finger tight and use a hammer to tap it in the rest of the way.

#9 If the trolley has moved one way or the other, reposition it to its original position and slide the motor housing back over the shaft, then secure. Plug the 4 pin connector in all the way and give that big black circular cup a good push back on the shaft to make sure it’s on.

#10 Put the limit assembly back in.

#11 Replace the small gear and triton shaped keeper.

#12 Replace the cover and remove the vicegrips/c-clamps from the rail if need be. (If you replaced the whole gear and sprocket assembly, attach the chain or belt.)

#13 Plug in the opener and test. If the door is not travelling far enough up and down or too far up and down adjust the limits accordingly using a flat blade screw driver. The limits are located the on the left side of the opener. You will see two small circular holes. The hole closest to the door is the down limit. Turing this a half turn at a time towards the door will cause the door to close further. Turning it opposite will cause the door to do the opposite. The hole furthest away from the door is the up limit. Turning it away from the door will cause the door to travel further up and turning it towards the door will cause the opposite. You want the bottom of the door to be even to slightly above the header in the up position. You want a good tight seal at the bottom so want the door to hit the ground, then stop. Adjust the limits accordingly by a half turn each time. Continue until door stops in desired position.

Congratulations you did it!

You’ll notice left over pieces when your done. This is where my instructions differ from the manufacture’s. You are supplied with everything to replace the worm gear and all the bushings. I have never had a worm gear or its bushing go bad on me. Ninety Nine Percent of the technicians in my area perform the gear replacement as stated above. I have ran into one or two that perform the whole task. I have found that most the do it yourselfers end up doing more harm than good when trying to use everything supplied. The choice is up to you. My advice is save the extra parts in case you ever need them again. I highly doubt you ever will.