LiftMaster K75-39337 LA500 Trolley Nut / Traveler Carriage Service Kit

The LiftMaster K75-39337 is the trolley-nut service kit for the documented LA500 actuator-arm repair procedure. The supplier calls it a traveler carriage kit, while the manufacturer identifies the trolley nut and additional service pieces for damage associated with an impact or similar event. This is an internal arm repair, not a complete replacement actuator. Select it after the arm, drive screw and related components have been inspected, and review the manufacturer’s warranty guidance before deciding between a component repair and replacement of the arm.

Compatibility — Models, Versions and Exclusions

Evaluate Impact Damage Before Opening the Actuator

The manufacturer describes this repair for a trolley nut damaged by a vehicle strike or a similar event. Such damage may extend beyond the nut itself. Have the technician inspect the arm, gate attachments, housing and drivetrain before selecting a repair scope. A component kit should not be used to conceal a bent assembly or a gate geometry problem.

The service instructions emphasize tight factory tolerances and a clean working environment. Preserving alignment, seals and retained hardware matters throughout the repair. This is not a simple external bolt-on replacement. Review the complete procedure and equipment needed before disassembly, then complete the required setup and safety testing with the repaired arm installed in the approved system.

Specifications and Product Identification

Before Ordering

• Identify the exact LA500 arm and service-kit revision.
• Inspect the gate and actuator for additional impact damage.
• Review warranty status and the manufacturer’s arm-replacement guidance.
• Confirm the complete kit inventory, retained hardware and required shop procedure.

Package Contents and Separate Requirements

The manufacturer inventory identifies a trolley nut and additional pieces such as bearing and retention components, trolley plates, a base plate, arm gasket and fasteners. Confirm the current carton against the kit instructions rather than assuming every internal arm part is supplied. A complete motor, drive screw, control box and replacement actuator are not promised as included.

Safety Warnings — Read Before Installation or Service

• WARNING: A disconnected actuator can leave the gate free to move. Secure the gate and use a qualified gate technician before removing or servicing the arm.
• Disconnect power and battery as directed before service. Keep the work area clean and prevent unintended movement during any prescribed testing.
• Do not force or modify tightly aligned drivetrain parts to approximate the original fit. Preserve seals and the specified assembly method.
• Complete the manufacturer’s recommissioning, travel, reversal and entrapment-protection tests before returning the gate to use.

Related Products and Important Differences

• LMRRUL monitored photo eye — a separate protection option only where the exact operator and control revision approve it; not a universal legacy retrofit.
• LMWEKITU monitored wireless edge kit — a separate edge communication system for approved controls and resistive edges; not a replacement for this mechanical or electrical service part.

Frequently Asked Questions

Is this a complete replacement actuator?

No. It is an internal trolley-nut service kit for the documented LA500 repair.

Does it fit LA400 or LA412?

No compatibility is established for those different actuator families.

Can a new nut repair every arm damaged by a vehicle?

No. The housing, drive screw, attachments and alignment need inspection for additional damage.

Could this repair affect an existing warranty?

The manufacturer warns that the procedure may affect arm warranty coverage and advises considering arm replacement while covered.

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.