The LiftMaster 109B18 Inner Trolley Shaft is a genuine OEM replacement part for LiftMaster chain drive garage door openers. Positioned within the trolley assembly, this shaft helps link and guide the inner trolley along the rail so the opener can pull and release the door smoothly. Replacing a worn or damaged inner trolley shaft restores proper travel of the carriage, reduces slippage or binding, and maintains reliable day‑to‑day performance in residential garage door systems.
This part is used on select LiftMaster chain drive models; always confirm compatibility by checking the parts diagram for your exact opener model and serial range. Installation is mechanical and typically involves disconnecting power, releasing the door from the opener, relieving chain tension, and swapping the shaft within the trolley assembly using the original fasteners or clips per the manufacturer’s service instructions. After reassembly, re‑tension the chain and verify travel limits and safety reversal. No radio control or logic board programming changes are ordinarily required for this replacement. For safe results, ensure the door is properly balanced and follow LiftMaster guidelines or consult a qualified technician.