LiftMaster 3840 Screw Drive Replacement Parts
LiftMaster 3840 Replacement Parts
The 3840 is a DC screw drive opener with battery backup. It differs from the earlier LiftMaster screw drives in several places — it uses a positioning sensor rather than an RPM sensor, and it has its own trolley assembly. Check the part numbers below rather than assuming a part from another screw drive fits.
Beeping, running slowly, or dead during a power cut? On a 3840 that is almost always just the backup battery. The G485LM 12V battery is the part, and it is the cheapest fix on this page. See section 2.
1. Motor Unit
First part of number below corresponds to key number above:
| Key | Part # | Description |
|---|---|---|
| 01 | 41C588 | Drive shaft cover |
| 04 | 41A6790 | Wire harness kit |
| 06 | 041C6551 | Positioning sensor |
| 09 | 041A6231 | End panel |
| 10 | 041C0213 | Transformer and harness |
| 11 | 31D504-20 | Cover |
| 13 | K108D0079M | Light lens |
| 14 | 175B88 | Light socket |
| — | 041A6262 | Complete trolley assembly |
The 3840's trolley is the 041A6262 above — not the 041C4677 used on the older screw drives, which is discontinued in any case.
Parts we cannot supply for the 3840. Both logic boards are discontinued — the 41DS002-2 and the 390 MHz 041DS002-2-390 — and so are the line cord (41B135) and the drive belt (041B0024). Everything else on the diagram is available. If your board or drive belt has failed, call (866) 965-5599 before ordering anything else — we will tell you honestly whether the repair is worth doing, and you can see current replacement garage door openers if it is not.
2. Battery Backup and Bulbs
| Key | Part # | Description |
|---|---|---|
| — | G485LM | 12V replacement battery for the backup system |
| — | LMLED1 | Universal replacement LED bulb, vibration rated |
A backup battery that no longer holds charge is a consumable, not a fault — expect to replace it every few years. The opener will run normally on mains with a dead battery, it just will not work during an outage.
3. Screw Drive Rail
First part of number below corresponds to diagram number above:
| Ref | Part # | Description |
|---|---|---|
| 01 | 041A4795 | Hardware bag |
| 04 | K081C0168 | Rack |
| 04 | K081C0275 | Rack — second version |
| 06 | 041A4836 | Drive sprocket kit |
| 07 | K025C0020 | Coupler |
| 16 | 041B0035B | Curved door arm |
| 17 | 4178B0034B | Straight door arm section |
| — | 041A4837-1 | Worm gear and retainer kit |
| — | 83A11-2 | Rail grease |
| — | 041A8094 | Door arm kit — curved and straight sections together |
| — | 041A2770-17 | Installation hardware kit |
There are two racks at ref 04 — K081C0168 and K081C0275. Check the number on the one you are removing. A screw drive rail that binds or runs noisily usually just needs cleaning and re-greasing with the 83A11-2 above; strip the old hardened grease off first rather than adding to it. See all screw drive rail parts.
4. Safety Sensors and Brackets
First part of number below corresponds to diagram number above:
Current parts — order these
| Ref | Part # | Description |
|---|---|---|
| S1–S2 | 041-0136 | Safety sensor eye kit — sending and receiving eyes, supplied as a matched pair |
| S3–S4 | 041A5281-1 | Sensor extension brackets |
| — | 041-0155-000 | Safety sensor brackets, 2021 to present |
| — | 041B0873 | Sunblocker bracket — stops sunlight false-tripping the eye |
| — | Sensor Guards | Protective guards, sensors not included |
| — | 041B4494-1 | 2 conductor bell wire, 26 ft |
Superseded part numbers
The current eyes and brackets replace every earlier version, so there is no need to match your old part number — order the current part.
| Old Part # | Order Instead | Notes |
|---|---|---|
| 41A5034 | 041-0136 | Eye kit used 1997 onward, now superseded |
| 12B484 | 041A5281-1 | Square holed mounting bracket, discontinued |
| 12B485 | 041A5281-1 | Slotted mounting bracket, discontinued |
| 041A5266-1 | 041-0155-000 | Sensor mounting bracket, no longer available |
5. Remotes, Wall Controls and Door Hardware
First part of number below corresponds to diagram number above:
| Ref | Part # | Description |
|---|---|---|
| 01–02 | 893MAX | 3 button visor remote — universal replacement for all older remotes |
| 03 | 10A20 | 3V coin battery for the remote |
| 05 | 10A14 | 12V battery — 61LM series remotes |
| 06 | 041B4494-1 | 2 conductor bell wire, 26 ft |
| 07 | 041A4353 | Header bracket, 1993 to current |
| 08 | 041A5047 | Door bracket |
| 09 | 041A2828 | Manual release rope and handle assembly |
| 10 | 29C128 | Remote visor clip |
| 12 | 041A4166 | Lighted pushbutton, two wire |
| 13–15 | 889LM | MyQ control panel — the replacement on 1998 and newer openers |
| — | 041A4202-6B | Wall control panel, two wire |
| — | 041A3504 | Antenna extender kit |
| — | 041A3504-1 | Antenna extender kit with adapter |
| — | L6950 | Multi purpose spray lube, green |
| — | L6960 | Multi purpose spray lube, blue |
Remote controls
The original remotes for these openers are discontinued. The 893MAX is the universal replacement and works with all the older LiftMaster, Chamberlain and Craftsman openers. It covers 371LM, 971LM, 973LM and 893LM, and is the listed substitute for 81LM, 83LM, 63LM, 753CB, 850CB, 853CB, 953CB, 953EV and Craftsman 53680, 53859 and 53879. Browse all LiftMaster remote controls.
Wall controls — superseded part numbers
| Old Part # | Order Instead | Notes |
|---|---|---|
| 98LM | 889LM | Motion detecting control panel, discontinued |
| 398LM | 889LM | Control panel, discontinued |
| 888LM | 889LM | Control panel, discontinued |
More LiftMaster Parts
All screw drive rail parts · All LiftMaster opener parts · LiftMaster remote controls