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.
Getting out the gear shafts
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Photo 1: Remove the chain
Unscrew the outer nut on the chain tensioning rod. If necessary,
use pliers to prevent the chain from turning. Then slip on a pair of
gloves and remove the greasy chain from the sprocket at the top
of the opener.
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Photo 2: Remove the helical gear assembly
Unscrew the hex-head screws that hold the helical gear assembly
in place. Save the screws for reassembly. Then lift the entire
assembly (sprocket, plate, shaft and helical gear) up and out of
the top of the unit.
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.
Remove the helical and worm gears
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Photo 3: Remove the helical gear from the shaft
Support both ends of the helical gear assembly with the two jigs. Hold a small drift
punch over the roll pin and tap the pin out of the shaft with a small hammer.
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Photo 4: Remove the worm gear
Loosen the collar setscrews with a hex wrench and slide the worm gear off the shaft.
Then remove the motor retaining screws.
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.