If you press the garage door opener button and hear either a humming or a grinding sound, but the door won’t open, you may think you need a new opener. And you might. But before you give up on the old unit, pop off the cover and check for stripped gears. That’s a common problem and one that you can fix yourself for way less than the cost of a new opener.
You’ll have to get a replacement gear kit (two new gears, grease and washers), which may take some running around. But once you have the kit in hand, you can do the repair in about two hours. You’ll need a 2x4, a small drift punch, a standard 1/4-in. drive socket set, hex wrenches, a circular saw, a drill and a hammer. I’ll show you how to remove and replace the gears without damaging the shafts.
Start by unplugging the opener. Then remove the retaining screws for the metal cover and put it aside. Shine a flashlight directly at the gear set. If you see chewed-up teeth, you’ve nailed the problem. If the gears are in good shape, you’ve got a more serious problem and your best bet may be to just replace the entire unit. To find a replacement gear kit, write down the make, model and serial number of your opener (you’ll find it on a label on the back of the opener). Then call a garage door opener repair company. It’ll probably charge a bit more than an Internet site, but at least you’ll have the parts right away and be up and running the same day.
Use a combination wrench to loosen and remove the chain (Photo 1). Next, use a 1/4-in. drive socket, extension and ratchet to remove the helical gear assembly retaining screws (Photo 2). Take a digital photo of the wiring connections from the motor or label them with masking tape. Disconnect the motor wires and remove the entire motor assembly. Move the helical gear assembly and the motor assembly to your workbench.
Cut a shallow groove into a 2x4 with a circular saw. Then slice off about a 3-in. section to make a jig to hold the helical gear assembly circular plate (Photo 3). Place the plate in the groove, hold the gear assembly level and mark the end of the shaft on another 2x4. Drill a hole in the wood and insert the end of the shaft. Then remove the roll pin (Photo 3). Slide the old gear off the shaft and replace it with the new gear. Reinstall the roll pin using the same jigs.
Next, remove the retaining collar and thrust washers on the end of the motor shaft (Photo 4). Pull the motor out of the chassis and slide the worm gear off the shaft (the roll pin stays in place on this shaft). Slide on the new worm gear with the notched end facing the roll pin.
Reassemble the motor assembly and place it back in the opener. Then install the helical gear assembly. Coat the gear teeth with new grease. Reattach the chain and tighten it to the proper tension (see your owner’s manual). Test your repair with the garage door disconnected from the opener trolley.