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Toyota Maintenance: Servicing the Aisin Manual Hubs

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Joe Micciche - June, 2000

The hub parts: 1) handle; 2) cover; 3) gasket; 4) hub body; 5) handle snap-ring, spring, and steel ball; 6) cover bolts; 7) O-ring seal; 8) tension spring, pawl, spring; 9) clutch.

The Aisin manual hubs on the Toyota 4-wheel drive trucks are regarded as the best hubs going, and they are a great swap for those with automatic hubs or ADD flanges. With some basic maintenance, these hubs will remain watertight, and they will provide years of reliable service. For this article, I tore down a hub I bought from a junkyard to use as a trail spare: I wanted to make sure it was ready for use.

The first step in tearing down the manual hub is to remove the hub cover. With the hub set to "Free", remove the six 10mm bolts which hold the cover on to the hub body. Remove the cover, the gasket, and separate the hub body from the rotor (for a complete explanation of removing and replacing hubs, see the article Toyota Front End Maintenance - Disassembly).

When the hub body is off, pull the clutch and tension spring from the body, and remove the spring from the cover. Make a note of how the springs, pawl, and clutch are installed, as they must be reassembled in the same manner.

Under the hub cover, a snap ring keeps the handle in place. This snap ring can be removed with needle-nose or snap-ring pliers. Upon removing it, the handle can be separated from the cover. Be mindful of the tiny steel ball and spring in the handle: if these pieces are lost, some improvisation will be necessary to replace them. Also check the O-ring seal around the handle: if it's ragged or worn, it should be replaced.

At this point, clean and inspect all of the parts of the hub. If any water, grit, or other foreign material is in the hub, it should be thoroughly inspected for other flaws. Tearing down the hub body is not required, as long as proper operation is verified and the old grease is removed.

After cleaning and prior to reassembly, everything gets a coat of grease.

With everything cleaned, start reassembly by placing the spring and steel ball into the handle, then place the o-ring seal on the handle. Lightly grease the surfaces on the handle, including the outer edge where it rides on the cover, and the spring seat. Then place the handle into the cover by lining up the steel ball with the detent in the cover and seating so the hub is in "Free". Compress the snap ring and install it, then check for proper operation of the handle in the cover.

Seating the clutch and springs on the handle. The spring, in this shot, came out of the guide inside the clutch.

The tension spring is then installed in to the clutch. The spring end should be aligned with the groove in the clutch, and the pawl placed over the spring (if disassembled) with one large tab holding the bent spring end. Then, with the large spring seated on the hub cover, compress the clutch on to the cover by aligning the tabs with the handle grooves.

This hub is ready to go as a trail spare.

Grease the clutch, inner hub body, and the splined sleeve prior to reinstallation, and place a gasket on the hub body. For a spare hub, at this point you can assemble the cover to the hub body; or if this is an on-vehicle service, the hub body should be installed on the rotor prior to installing the cover. The cover and clutch will slide into the body with the pawl tabs in the slots without any teeth, and the entire assembly should be checked for proper operation. If it doesn't work, pull the cover/clutch off and realign them. If it does, torque the cover bolts down to 7 ft. lbs. and wrap it up!


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