The arm restraint gear is the small toothed steel piece inside each swing-arm pivot on a two-post lift, and it does the job its name suggests: it locks the arm in position so it cannot swing out from under a vehicle once the load is picked up. It is a part almost no one thinks about until an arm feels loose at chest height, and then it becomes urgent. This page explains what the gear does, how to spot a worn one, and how the parts differ across Rotary, Challenger, BendPak, and Forward two-post lifts, so you can order the correct replacement and get the bay back into service.
What arm restraint gear does on a 2-post lift
On a two-post lift each swing arm rotates on a vertical pin at the carriage. Sitting on that pin is a round steel plate cut with teeth around its circumference — the restraint gear — and a spring-loaded pin drops into the teeth to lock the arm’s angle. As the carriage rises off the floor the restraint engages automatically; as the carriage lowers back down and the arm can safely swing, the pin lifts clear. The arm restraint gear is what actually holds the arm against side-loading forces once a vehicle is in the air, which is why ALI standards require the mechanism on every certified two-post lift.
Signs the gear is worn
Four symptoms point straight at gear replacement. First, an arm that swings freely at full rise when it should be locked — the engagement pin is riding on top of the teeth instead of dropping between them. Second, an audible clicking or ratcheting as the arm is nudged; the pin is skipping across rounded teeth. Third, visible chipped, broken, or missing teeth when you look down at the gear from above. Fourth, arms that hold at first but slowly rotate under load, indicating rounded-off tooth flanks. Any one of these is a reason to replace the gear, the pin, and the spring as a set — do not mix new components with worn ones on the same pivot.
Rotary arm restraint gear (S130105 family)
The classic Rotary arm restraint gear across the SPO7, SPO10, SPOA10, SPO12 and related SPOA families is the S130105 style plate, sold with a matching engagement pin (often S130106) and torsion spring. Rotary uses effectively the same gear geometry across a very wide model range, which makes cross-reference straightforward when you have the model and serial number. Later-generation Rotary lifts and some SPO16/SPO20 heavy-duty models use a larger-diameter gear with more teeth for stiffer locking, so verify by measurement, not by model name alone. The Rotary gear kits are stocked in our Rotary aftermarket parts hub.
Challenger arm restraint gear
Challenger two-post lifts (CL10, E10, CL12, CL15, CL16, CL18, and the newer commercial family) use their own restraint geometry with Challenger-specific part numbers. Function is identical to the Rotary design — a toothed plate and a spring-loaded pin — but Challenger gears are not interchangeable with Rotary, so match to the model. Challenger sells the restraint as a service kit that includes the gear, pin, spring, and hardware for one arm; you usually order four kits at a time and rebuild every pivot on the lift, because if one gear is worn the others are on the same clock. Kits are in our Challenger parts hub.
BendPak, Forward, and older lifts
BendPak two-post lifts use a similar restraint concept with a smaller-diameter gear and often a molded-in nylon collar that quiets the ratchet. Forward two-post lifts share a common restraint family with several Rotary designs due to shared corporate history, but the specific gear part number is Forward-branded and should be ordered by Forward model. Older shop lifts from Ammco, Weaver, and Wheeltronic used their own gear geometries; some are still supported, some are not, and the honest answer on a very old lift may be that the gear is only available as a full pivot assembly. Our other-brand lift parts hub is where these live.
How to identify the gear on your lift
The reliable way to identify a restraint gear is a photograph plus three measurements: outside diameter across the teeth, tooth count, and the center-bore diameter that fits over the pivot pin. The lift’s model and serial number narrow the search, and the photograph settles which revision your carriage uses. Our parts lookup filters restraint gears by lift model, and if you are unsure the 2-post lift parts guide walks the identification of every mechanical part on the carriage.
Field replacement and do all four at once
Replacing the part is field-doable. Lower the lift to the floor so the arms can be supported. Remove the arm pin retainer and swing the arm out until you can lift the arm off the pivot. The gear sits on top of the pivot; note orientation, remove the engagement pin and spring, drop the old gear off, clean the pivot bore, install the new gear and spring, land the arm back on the pin, and reinstall the retainer with new cotters or bolts to spec. Cycle the arm through its range to confirm the pin drops cleanly into every tooth, then rise-test empty before you put a vehicle on it. Two-post lifts have four arms and four gears — if one is worn the others have seen the same cycles, so order all four kits and rebuild every pivot in one visit.
Compatibility across ALI standards
Any lift certified to ALI ALCTV requires a working arm restraint, and any repair that removes or bypasses one voids that certification and shop insurance in most jurisdictions. Use the manufacturer-spec part, not a generic look-alike, and do not modify the engagement geometry. Related mechanical safety parts — pawls, latches, and release cables — are covered in our car lift parts buyers guide.
Ready to order the correct arm restraint gear for your lift, or want us to confirm the fitment before it ships? Call Auto Lift Services at 800-674-9302. Tell us the brand, model, and serial number and, ideally, send a photograph of the existing gear; we will confirm the right kit, ship it out, and keep your bays in service.
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