Recently, I replaced the drive gear on my Sears Craftsman chain-operated garage door opener. Over 90 Crafstman garage door openers use the same drive gear (part number 41C4220A). So there must be a fair number of people googling this part number looking for advice on the replacement process. The manual that comes with the part has decent info. This page on dropbox.com has great photos and very detailed information. This blog post is reserved for my pointers. Do yourself a favor and pay the extra ten bucks for the drive gear assembly which is part 41C4220A. Don’t get part 41A2817 which is just the drive gear and worm gear. It’s a lot easier replacing the whole drive gear assembly.
First off, you’re going to need a 1/4″ socket wrench (with a 5/16″ socket) if you’re replacing just the drive gear and not the worm gear. A 1/4″ adapter on a 3/8″ wrench won’t work for the screw that’s above the worm gear. There’s no room for a wrench with an adapter.
But before you start sticking a socket wrench inside the opener, be sure you pulled the plug on the unit. You could set off a nasty spark if the wrench touches to wrong part of the opener. I did that. (moron, yes). And make sure the chain is off the drive gear.
In addition to removing the three screws holding down the drive gear, the plastic rectangle at the bottom needs to be snapped off. And the tiny gear at the bottom will need to slide off. Then the whole unit is easily removed from the top if there’s enough room above your opener.
Before you grease up all the gears, do a dry fit of the screws in your new drive gear. The holes are not threaded. They become threaded when you drive the screws through, so it will take a fair amount of pressure to do so. It’s easier to do this on drive gear when the holes are easily accessible.
Grease up the gears. Place the new drive gear. Screw it in place. Slide on the new tiny gear at the bottom and snap the plastic rectangle to hold the tiny gear. Put the chain back onto the drive gear. Plug in the garage door opener. Test your handiwork and you should be in back in order.