The LiftMaster 041A6689 Inner Trolley Shaft for belt-drive garage door openers is a genuine replacement component designed to restore smooth, reliable travel of the door along the opener rail. This inner trolley works in tandem with the outer trolley on belt-drive rails, coupling to the door arm and engaging with the manual emergency-release mechanism (red cord) so you can disengage and re-engage the door when needed. It is intended for select LiftMaster and Chamberlain residential belt-drive openers that use a two-piece trolley design; always verify compatibility by matching part number 041A6689 in your opener’s manual or parts diagram.
Use this part to resolve issues such as failure to reconnect after pulling the release, inconsistent carriage engagement, or excessive play in the trolley linkage. Installation is mechanical and typically requires disconnecting power, pulling the emergency release to open the drive, removing the retaining pins from the old inner trolley, sliding it off the rail, and installing the new unit in the same orientation before testing door travel and safety reversal per the opener manual. No programming is required. This OEM replacement is for belt-drive rails only and is not intended for chain-drive systems; ensure proper alignment and secure pinning during installation to maintain safe, dependable operation.