The LiftMaster 81B170-1 Shaft Limit Worm is a genuine limit-assembly component for select LiftMaster commercial door operators. This worm-driven shaft meshes with the limit mechanism to rotate the open and close cams, allowing the operator’s limit switches to stop the door accurately at its travel endpoints. Use it as a direct replacement when the existing limit worm is worn, stripped, or damaged—common causes of drifting limits, overtravel, or inconsistent stop points on jackshaft and trolley-style commercial garage door operators.
Compatibility varies by operator model and revision; confirm by checking your operator’s parts diagram or service manual for part number 81B170-1 before ordering. Installation should be performed by a qualified technician under lockout/tagout: disconnect power, remove the limit housing cover, note cam positions, replace the shaft limit worm, then reset and test the open/close limits and safety devices per LiftMaster procedures. This OEM-style replacement supports reliable travel control in commercial applications where a mechanical, worm-driven limit system is used, and is not intended for units equipped with electronic or absolute encoder limit systems.
Compatible with LiftMaster 2110, 2220, 3110 and 3220 models