LiftMaster 71-1550B40LGH Drive Sprocket — 40 Teeth, #50 Chain, 1-Inch Bore
LiftMaster 71-1550B40LGH Drive Sprocket — 40 Teeth, #50 Chain, 1-Inch Bore
The LiftMaster 71-1550B40LGH is a 40-tooth drive sprocket for #50 roller chain, with a 1-inch bore and a 1/4-inch keyway. It is a replacement mechanical drive component for an assembly that specifies this exact sprocket configuration. Match the complete part number, shaft size and original drive arrangement before ordering. Tooth count and bore size both matter: a sprocket that accepts the same chain can still have the wrong shaft fit or alter the original drive ratio.
Compatibility — Models, Versions and Exclusions
| Model or selection point | Compatibility requirement |
|---|---|
| Exact documented replacement | Use where the equipment parts list specifies this complete reference or an approved equivalent. |
| #50 chain | Correct chain family, but chain size alone does not establish operator or shaft compatibility. |
| 71-1550B40QGH | Also 40 teeth for #50 chain, but has a 1-1/4-inch bore; not the same shaft fit. |
| Other tooth counts or bore sizes | Do not substitute without approval for the complete drive assembly. |
Match Shaft Fit and Drive Geometry
This 40-tooth LGH version has a 1-inch bore. Do not confuse it with the 40-tooth QGH version, which has a 1-1/4-inch bore, or with a 32-tooth sprocket that changes the drive ratio. An aftermarket sprocket with matching headline dimensions also needs its hub and retention details checked. The full LiftMaster service reference is the preferred starting point for a like-for-like repair.
The sprocket must sit in the correct chain line and be secured by the specified shaft, key and retention arrangement. Have the technician inspect the shaft and keyway for wear as well as the teeth. A damaged shaft, loose mounting or misaligned chain can cause recurring trouble after a new sprocket is installed. Photograph the existing assembly before parts are removed so its position and neighboring components can be identified.
Specifications and Product Identification
| Specification | Details |
|---|---|
| Manufacturer part number | 71-1550B40LGH |
| Sprocket designation | 50B40 |
| Tooth count | 40 |
| Chain family | #50 roller chain |
| Bore diameter | 1 inch |
| Keyway | 1/4 inch |
| Retention detail | Manufacturer part description specifies set-screw retention; confirm supplied hardware |
Before Ordering
- Record the complete operator model and the sprocket part number from its service diagram.
- Confirm 40 teeth, #50 chain, a 1-inch shaft fit and the specified keyway.
- Check hub clearance, chain alignment and the required shaft-retention arrangement.
- Inspect the chain, connecting link, mating sprockets and shaft for related wear.
Package Contents and Separate Requirements
This listing identifies the sprocket. Do not assume that roller chain, a connecting link, shaft key, shaft or every mounting fastener is included. Verify the current supplier package and obtain the separate components needed for the repair. The set-screw reference is a retention detail; it should not be interpreted as a stainless-steel material specification or a corrosion-resistance guarantee.
Safety Warnings — Read Before Installation or Service
- WARNING: An exposed chain drive can trap fingers or clothing and cause serious injury. Replacement requires a qualified door- or gate-systems technician.
- Isolate and secure all applicable power sources and prevent unexpected movement before working on the chain drive.
- Do not change tooth count, enlarge the bore or improvise the shaft connection to make an unmatched part fit.
- Restore guards, verify chain alignment and complete the equipment’s prescribed operating and safety tests before returning it to service.
Related Products and Important Differences
- #50 roller chain, 10-foot length — a chain-family match; determine the required length and installation suitability.
- #50 chain master link — select the correct connecting link for the actual chain; not interchangeable with a #41 link.
- 50B40 40-tooth sprocket with 1-inch bore — a dimensional comparison from another listing, not a verified interchangeable LiftMaster service kit.
Frequently Asked Questions
Will any #50 sprocket fit?
No. Chain size, tooth count, bore, keyway, hub clearance and the approved drive arrangement must all match.
Can I change tooth count to make the opening move faster?
Do not use a service replacement to change operating speed. Any ratio change requires approval for the complete equipment and its safety system.
Should I inspect the chain at the same time?
Yes. A technician should evaluate wear, alignment and the mating components so a worn chain does not undermine the repair.
Does this listing include a shaft key and new chain?
These are not promised as included. Confirm the supplied contents and order the separately required parts for the documented repair.
Need Help Confirming the Right Product?
Contact Garage-DoorParts.com before ordering. Send the full equipment model, readable part labels and photographs of the installed assembly. Include the dimensions, electrical configuration or accessory details relevant to your project so the listing can be checked against the actual installation.
Details
Need Help With Compatibility?
Not sure if this is the correct part for your garage door, operator, gate system, or application? Contact Us before ordering — we’re happy to help.
Garage-DoorParts.com carries a large selection of residential and commercial parts, and many components can look similar while having important differences in dimensions, model numbers, voltage, mounting, or compatibility.
For the best assistance, please provide as much information as possible, including the manufacturer, model number, part number, door or operator type, dimensions, and clear photos of the existing part or equipment.
Our goal is to help you identify the correct product before you order and reduce the possibility of ordering an incompatible part.
Contact Us with your product questions and compatibility information, and we’ll do our best to point you in the right direction.
Shipping & Returns
We strive to process and ship all orders in a timely manner, working diligently to ensure that your items are on their way to you as soon as possible.
We are committed to ensuring a positive shopping experience for all our customers. If for any reason you wish to return an item, we invite you to reach out to our team for assistance, and we will evaluate every return request with care and consideration.
Shop The Full Collection
