Garage Door Opener Sprocket Broke Off – Replacing Gear & Sprocket

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An improperly balanced garage door or a tightly hung chain can break the sprocket on the garage door opener.

Even though the replacement kit comes fairly cheap, hiring a professional to replace it would end up costing you hundreds. So, if your garage door opener sprocket broke off and you are thinking of DIY-ing the replacement, you came to the right place.

garage door opener sprocket broke off

How to replace gear and sprocket kit on your garage door opener

If the gear and sprocket kit of the door opener has indeed broken off, here’s how you can replace it with a new one purchased.

Step 1 Cut off the power supply by removing the cord from the outlet and taking off the outer panel.

Depending on your model, you might need to take off the whole exterior or just the bottom and top portions. See the manual of your door opener unit to ensure you are taking off the right panel.

Step 2After you remove the outer panel, you have a few more screws to access the metal and plastic gear for the garage door opener.

The metal gear-like part actually is the sprocket, in case you didn’t know already. However, if the plastic gear at the bottom has broken, you’ll have to buy the whole sprocket and gear kit as they come as one unit.

Step 3 – To ensure you reassemble the chain and gear correctly, you can mark a point on the chain and the metal hanger it hangs over and use the markings to adjust the position later on.

Step 4 – Next, you’ll have to disengage the trolley. Be careful with this as disengaging it incorrectly can lead the garage door or the trolley-adjacent parts to free fall.

Most units have a simple pull mechanism to disengage the trolley. Make sure you know what you are doing before you pull out the engagement point.

Step 5Take a vice grip or any other tool that can firmly hold the chain to the metal hanging.

This way, you can ensure the chain doesn’t go off its position too much. Otherwise, you’ll end up adjusting the limiting point after the reassembly, which can be challenging if you have an improperly balanced door.

Step 6 – As the chain is firmly attached and the trolley disengaged, loosen the nut that tightens the chains along with the sprocket. Loose only as much as needed to take the chain off the sprocket.

Step 7If your sprocket has a cover, make sure to remove it to access the chain-sprocket engaging points.

Step 8 – Once the chain is loose enough and the sprocket cover is off, take out the chain from the sprocket, freeing up the gear and sprocket kit for replacement.

Step 9Remove the nuts and screws holding the kit on the garage door opener housing. Carefully store the screws and nuts.

Step 10 – Once unscrewed, take the old gear and sprocket kit off the housing. Clean the debris and old residual grease from the housing.

Step 11 – To ensure the sprocket-gear works smoothly, put new grease on the parts, both metal and plastic. Also, grease the areas where the kit will connect to the housing, including the bushing and warm gear.

Step 12Put the new kit inside and screw it. Tighten it to make sure the kit doesn’t move inside the door opener housing.

Step 13 – Next, put the chain back on the sprocket and make sure the marking on the chain and the adjacent metal hanging aligns perfectly.

Step 14 – Before you tighten the nut you had loosened earlier, make sure there are no twists or turns in the chain.

If you tighten the chain with a twist within the chain, it might snap off during operation. Also, make sure there’s a little sag in the garage door opener chain. A tightly wound chain can also snap during closing or opening the garage door.

Step 15Take the vice grip off and reengage the trolley. Reassemble the panel and put back the screws and nut.

Step 16Connect the power line back to the opener unit. Now try opening and closing the garage door multiple times to check if the limits need to be adjusted.

Also, make sure the garage door is balanced correctly. If they aren’t adjusted or balanced, the sprocket might break off again.

3 common reasons for garage door gear kit to break

If you are wondering why my garage door opener sprocket broke off, here are the three most common culprits.

  1. Tightly Wound or Sagging Chain: If the garage door opener chain is too tightly wound, the chain can snap off during operation along with the sprocket it is attached to. Sagging of the chain can also lead to sprocket breakage during closing or opening the door.
  2. Unbalanced Garage Door: Garage doors tend to become unbalanced after years of opening and closing as the door starts to tilt. So, if your garage door opener sprocket broke off, make sure to check the door.
  3. Crooked Chain: Crooked chain or tilted chain can strain the sprocket when operating, causing it to break.


1.      How much does the garage door sprocket replacement cost?

If you are DIY-ing the replacement, the cost is simply the price of the gear and sprocket kit. Kits like the u003cstrongu003eu003ca href=u0022;linkCode=ll1u0026amp;tag=garagestoragelab1971-20u0026amp;linkId=f538a4d2edd1e4db4f6ef3cd10a6effdu0026amp;language=en_USu0026amp;ref_=as_li_ss_tlu0022 target=u0022_blanku0022 rel=u0022noopeneru0022u003eLiftmaster Chamberlain garage door sprocket replacement kitu003c/au003e only costs $25-$30u003c/strongu003e.

2.      Can I hire a professional to do the replacement?

Yes, you can. But if you want to hire a pro to do it for you, the cost will be in the hundreds.

3.      Do I need to adjust the limits after replacing them?

Yes, you might need to adjust the limits if you haven’t put back the chain as it was.

4.      How do I know if it’s broken?

If the sprocket or gear is broken, the garage door won’t function properly, and you’ll hear noticeable noise.


Now that you know how much a replacement kit costs and how to replace the unit, you are ready to replace it on your own.

But as mentioned before, the disassembly is different for each model, and if you are not confident about yours, there’s no shame in calling a professional to take care of it.

Hi, I am Brent Hartman. I am a DIY enthusiast and love to improve and organize the garage in the most innovative way. I created this website out of my passion for helping people organize their garages.

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