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Tacoma Traction: 4.88 Gears And An ARB Air Locker For Our 2017 Toyota Tacoma

Posted in How To: Transmission Drivetrain on June 6, 2018
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Photographers: Evan Gage

Sure, the lift, wheels, and larger tires made our ’17 Tacoma look sharp and increased off-road dexterity, but once we got the truck out on the trails, it was no surprise when we realized that the truck would benefit from new axle gears and a front locking differential.

The ARB Air Locker was the solution to our frontend traction problems. The pneumatic locker is activated by an in-cab switch and uses compressed air to lock the differential, making sure that when activated, the front wheels spin at the same speed. Not only does this keep the Tacoma moving when traction is less than favorable, but the air compressor gives us the ability to reinflate our tires after a day of wheeling at lower pressures.

The larger 35-inch tires also meant the factory 4.30:1 axle gear ratio was no longer packing the punch we needed to crawl at slow speeds. The goal of regearing the axles on a rig that also sees the highway is twofold. You want a deep enough gear to provide the low-end torque necessary to spin larger tires at slow speeds while still maintaining a reasonable engine rpm on the highway. Right in the middle of the torque-to-reasonable-highway-rpm spectrum lies the 4.88:1 gear ratio. This gear combo from Nitro Gear & Axle also increased our crawl ratio from 39.8:1 to 45.2:1.

We headed to Rebel Off Road in Laguna Hills, California, to dig into our differentials and give our Tacoma the torque and traction it needed. Read on for some of the highlights of the install.

To begin regearing the rear, we removed the tires and wheels, disconnected the brakes and all associated wiring clips, removed the bolts from the third member, and slid out both axleshafts. The folks at Rebel Off Road told us many people neglect to disconnect this wheel speed sensor before they remove the axleshafts and subsequently break it.
We laid out the parts from Nitro Gear & Axle which included the new ring-and-pinion gears as well as all bearings and shims needed for the project.
With the carrier assembly removed and drained of oil, we marked and pulled the bearing caps (so we could reinstall them the exact same way later), took out the carrier bearings, and began unbolting the 12 fasteners holding the old ring gear to the carrier.
The old gears had a 4.30:1 ratio, meaning the old ring (on the left) had 43 teeth and the old pinion (also left) had ten teeth. The new ring gear (right) is thicker, but with 39 teeth, and it pairs with an eight-tooth pinion (right) for a 4.88:1 ratio.
It is always crucial to verify proper pinion depth. The pinion should contact the ring teeth squarely between the face and the flank of the tooth (refer to your installation manual).
After tapping the new ring gear into place with a dead-blow hammer, we applied red Loctite to the 12 bolts, and then torqued them to spec. We measured and set our backlash, set the preload on the pinion bearings, and reconnected the wiring for the stock electric locker. We recommend consulting a professional service technician or your installation manual for the exact torque specs for your application.
We bolted the carrier housing back to the axlehousing, reattached the rear driveshaft, and refilled the differential with 3.12 quarts of 75W90 GL-5 gear lube.
The front differential was not as simple as the rear, requiring us to remove the skidplate, both CV shafts, and many other cumbersome parts to access the differential assembly.
We fit the new ring gear around the ARB Air Locker using some precise taps from our plastic mallet. We then pressed on the carrier bearings and preloaded them with the included shim pack.
Next, we drilled through the differential housing, creating a hole that would eventually carry the air line from the compressor to the inside of the differential. We drilled with a 7/16-inch bit and tapped the hole with a 1/4-inch pipe tap.
After carefully laying the seal housing into the differential, we fed the seal housing tube through the drilled hole in the differential housing, marked the tube, and cut it roughly 5/16-inch from the end of the hole.
We tightened the bulkhead fitting into the differential housing with a 9/16-inch spanner, then sealed the fitting using the included O-rings, brass spacer, and thread sealant. After once again checking backlash and pinion contact, we reassembled the differential and shimmied it back to its original position under the Tacoma.
PhotosView Slideshow

To power the Air Locker, we began the process of nestling the ARB air compressor into the space under the Tacoma’s hood. We began by laying out all our parts, disconnecting the battery, removing the factory airbox, and mounting the compressor to the included tray using existing bolts in the body.

Following the instruction diagrams closely, we connected all 6mm air lines between the solenoid, the differential, and the compressor using the 1/8-inch nipples, push-in fittings, and sealant.
After attaching the air line to the bulkhead fitting, we ran the air line from the differential, along the transmission crossmember, and into the engine compartment. We made sure to avoid all moving or hot surfaces, and left enough tubing to accommodate suspension travel.
We then wired the rocker switches following the diagram included in the instructions. Everything fit snugly in the compartment to the left of the steering column, where the driver had already installed a switch for aftermarket lights.


Nitro Gear & Axle
Sacramento, CA
Renton, WA 98057
Rebel Off-Road
Lake Forest, CA 92630

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