This lock was grimy, so I stripped it down (which required filing away some staked metal), soaked all the parts in naphtha for a while, and then scrub-brushed each one so I could figure out how it works, and if it was repairable. Turns out there's virtually no damage under the grime that I removed, like nearly all other 3-screw autos I've collected.
IF THE IMAGE IS TOO SMALL, click it.
Disassembly:
1) After removing the lock body assembly from the hub, wipe the grease off. Rinse in solvent (naphtha, kerosene, mineral spirits, or parts cleaner) to remove as much residue as possible.
2) Remove the cam assembly from the hub; wipe & rinse it similarly.
3) Rotate the ramp until its slots align with the step so it comes out.
4) Gently compress the garter, extract it from the step, and separate the garter spring so all the cam pieces can be washed in solvent & scrubbed. FURTHER DISASSEMBLY IS NOT RECOMMENDED.
5) While submerged in solvent, rotate the drive spline & follower in the body until they align so the follower can be compressed against the wave springs, flushing solvent out of & into the lock body assembly until it flows out relatively clean.
Clean all parts thoroughly, scrub-brushing as needed to remove hardened grease, dirt, & rust scale. Wash in solvent, allow to dry, then apply a thin coat of disk-brake-rated (NOT marine) wheel bearing grease using a brush or by working mating parts together. Smooth & spread the grease by hand, and remove any excess. For final lubrication & any subsequent light cleaning, submerge the lock body assembly in ATF every 30Kmi.
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Today's free-running hubs are very simple to operate and feature seals that prevent the entry of dirt and moisture. Automatic locking hubs are used in many applications. They use the front axle shaft rotation to actuate a cam that locks and unlocks the hub.
There are two types of front hubs currently in use on Ford Trucks:
^ Manual (or free-running) that require the driver to get out of the cab to either lock or unlock them.
^ Automatic locking (they lock automatically when the axle shaft begins to turn).
The vehicle operator doesn't have to wait until the last minute (or when stuck) to lock the hubs. It makes sense to plan ahead and lock them at a convenient time. The hubs can be left in the locked position all the time if desired. For example, if the vehicle is constantly going from the highway to off the road conditions and back, it's not necessary to lock or unlock every time. If the vehicle is equipped with a manual shift transfer case and manual locking hubs, low range can be selected when the vehicle's front hubs are unlocked. This is useful for short distances if very low, creeper gearing (but not 4WD) is needed. For example, backing an empty boat trailer down a launching ramp is best accomplished in 2WD. Once the boat is loaded, 4L (low) can be selected to help pull the boat up the ramp. The hubs don't have to be locked for this purpose, and being in 2WD will prevent driveline windup while maneuvering in the boat ramp parking lot.
