Project 4Runner Backcountry Part 3

129 1103 Project 4Runner Backcountry Part 3 Arb Air Locker Unit

One of the best features of the fifth-generation 4Runner is the availability of a selectable rear locker straight from the factory. This option is one that can really help the 4Runner get into deep terrain, but our 4Runner isn't just going in to deep terrain on exploratory trips-it has to get out, too. To ensure we have maximum traction when we need it, we decided to add a selectable locker to the frontend.

129 1103 Project 4Runner Backcountry Part 3 4Runner On Lift

With the 4Runner secured on the hoist, we began the install by dismantling the frontend.

With a track record for ruggedness and reliability, we decided on the Air Locker from ARB. The Air Locker uses a fully machined differential case made from nodular iron, while many other components are made from the highest-quality aerospace-grade alloy steel. ARB designs the Air Locker to be stronger than other stock drivetrain parts and carries out destructive testing to ensure the end user gets the best possible product.

ARB's Air Locker works by replacing the stock open differential unit with the pneumatically operated ARB locking unit. A 12-volt compressor with a small air reservoir is wired and mounted to the vehicle and operated by a remote switch, usually mounted on the dash. A second switch, also mounted on the dash, opens a solenoid that releases pressurized air from the compressor reservoir, engaging the locking mechanism. Unlocking is as easy as depressing the switch, where the only noise you'll hear is the pressurized air venting to the atmosphere with a familiar "pssssh."

129 1103 Project 4Runner Backcountry Part 3 Front Diff

The 4Runner's front differential is very stout, featuring a cast-iron case and an 8.1-inch ring gear. The square chamber between the axle tube and housing is where the axle disconnect system resides.

The 4Runner's front differential is very stout, featuring a cast-iron case and an 8.1-inch

Able to lock and unlock the front end at the press of a button and while moving in a straight line up to 60 mph, the Air Locker is there when you need it, but invisible when you don't. When the locker is unlocked, it acts as an open differential, which means that around town and on the highway, there is no difference in how the 4Runner drives from stock, with no negative characteristics such as binding, popping or torque steer common to automatic locking differentials. This makes the Air Locker an excellent choice for the front of any vehicle, especially those that see use on pavement and off.

For the install, we headed down to Off Road Evolution in Fullerton, California, where we documented the installation of the Air Locker on Project 4Runner Backcountry.

Once the differential assembly was on the bench, we began to disassemble it.
After pulling the clamshell housing apart, we removed the factory carrier and the 3.727:1 gearing.
After pulling the clamshell housing apart, we removed the factory carrier and the 3.727:1
Next, we marked the shallow half of the clamshell case for the bulkhead port. ARB gives precise instructions on where to drill this hole.
Next, we marked the shallow half of the clamshell case for the bulkhead port. ARB gives pr

While the hole was being drilled, we fitted the seals in to the seal housing.
We then shaped the seal housing tube so that it would line up correctly with the bulkhead port.
We then shaped the seal housing tube so that it would line up correctly with the bulkhead
Once the seal housing tube was lined up correctly, we assembled the shim pack and placed both in to the bearing bore of the shallow half of the clamshell. We used a press to mate them with the clamshell.
Once the seal housing tube was lined up correctly, we assembled the shim pack and placed b

Turning our attention to the stock carrier, we then removed the factory bearings.
Next, we removed the factory ring gear from the factory carrier.
ARB recommends reusing the factory bearings on low-mileage vehicles like ours, so we installed them on the ARB differential.
ARB recommends reusing the factory bearings on low-mileage vehicles like ours, so we insta

Because our tire size increase was minimal, we kept the stock gearing. Here you can see the factory ring gear and bearings mounted on the ARB differential next to the stock carrier.
Because our tire size increase was minimal, we kept the stock gearing. Here you can see th
After cleaning the old RTV silicone off of the differential housing, we placed the new Air Locker assembly in the deep portion of the clamshell.
After cleaning the old RTV silicone off of the differential housing, we placed the new Air
Prior to final assembly, we used a dial indicator to check for proper ring and pinion backlash.
Prior to final assembly, we used a dial indicator to check for proper ring and pinion back

Once we were satisfied that the shim pack was thick enough to achieve the proper backlash, we used sealant on the differential housing mating surfaces for final assembly.
Once we were satisfied that the shim pack was thick enough to achieve the proper backlash,
With the two halves of the clamshell joined, we trimmed the seal housing tube and installed the bulkhead fitting.
With the two halves of the clamshell joined, we trimmed the seal housing tube and installe
Note the completed bulkhead fitting (arrow) in the photo of the differential housing being reassembled. After the differential was completed, it was remounted in our 4Runner, filled with oil and the front end was reassembled.
Note the completed bulkhead fitting (arrow) in the photo of the differential housing being

ARB's CKMA12 compressor kit includes everything you need for a clean install, including the wiring harness, fittings and this high-output 2.65cfm 12-volt compressor.
ARB's CKMA12 compressor kit includes everything you need for a clean install, including th
We had previously installed an sPod power distribution box in our 4Runner to manage our aftermarket electrical needs. The sPod allows you to wire up to six aftermarket accessories, without splicing into your factory wring, keeping the install cleaner and safer. With the sPod, you only have to run one wiring loom through the firewall and can easily add accessories at any time by connecting their power leads to the Source box under the hood.
We had previously installed an sPod power distribution box in our 4Runner to manage our af
Also available from sPod is this wiring harness that interfaces with the ARB wiring loom, allowing any sPod owner to easily control an ARB compressor and locker through the sPod system.
Also available from sPod is this wiring harness that interfaces with the ARB wiring loom,

Powering the ARB system was as easy as connecting the harness to the battery and the sPod pigtail to the sPod Source box.
Powering the ARB system was as easy as connecting the harness to the battery and the sPod
We mounted our ARB compressor in the front corner of the 4Runner. Here it is all wired up and plumbed in to the differential.
We mounted our ARB compressor in the front corner of the 4Runner. Here it is all wired up
The Air Locker supply line was run along the outside of the frame rail to clear the catalytic converter. With the wiring and plumbing complete, we were able to test the locker for the first time.
The Air Locker supply line was run along the outside of the frame rail to clear the cataly

We mounted our ARB switches on the center console in existing Toyota switch blanks so that they would be at our fingertips.
We mounted our ARB switches on the center console in existing Toyota switch blanks so that
The Spod does a tremendous job of cleaning up all the extra wiring we have from our aftermarket lights and ARB Air Locker system. As you can see, everything under the hood has its own place and for the most part, still looks stock.
The Spod does a tremendous job of cleaning up all the extra wiring we have from our afterm
The ARB Air Locker is available in over a hundred part numbers, ensuring that an application is available for your stock or modified 4x4.
The ARB Air Locker is available in over a hundred part numbers, ensuring that an applicati

SOURCES
ARB 4x4 Products 720 SW 34th Street Renton WA 98057 800-761-8192 http://www.arbusa.com	Off Road Evolution 1829 W Commonwealth Avenue Fullerton CA 92833 714-870-5515 www.offroadevolution.com
sPOD 661-755-8139 www.4x4s-pod.com