The quest to upgrade OR's project Toyota Tundra recently led us to Currie Enterprises in Anaheim, California. Since we'd already widened the track width of the Tundra with a new front suspension, we decided to take the same approach with the rearend. Deaver Spring's long-travel leaves gave us the travel we were looking for. However, the stock rear axlehousing was not only weak but narrow as well. Ray Currie had the answer in the form of the company's new CMAC housing.
The housing is a design taken from off-road racing's Trophy Truck class and is indeed one of the strongest on the market. The third-member housing takes its shape from several laser-cut steel plates, which are cut horizontally and welded together with internal gusset plates. This design stretches the size of the housing further outward onto the axle tubes, effectively strengthening them without any extra bracing. In short, it makes the axle tubes less susceptible to bending under the extreme loads that an off-road vehicle will generate when operating at high speeds over uneven terrain.
The housing is just one piece of the extremely durable and functional puzzle we had in mind. We had Currie fill the rearend with a 4.56 ring-and-pinion gearset from Precision Gear, and an ARB Air Locker. To put the power to the rear wheels, Currie machined a set of super-strong 35-spline axles, which fits to custom hubs and Explorer disc brakes. The axles were 1-1/2 inches longer per side, which stretched the rear track width to approximately the same width as the front suspension. This greatly improved the cornering stability of the truck.
In the end, a simple bolt-in installation to the rear suspension of our Tundra improved not only its durability, but also the truck's acceleration, traction, and braking. We'd yet to regear the stock rearend of this truck, so the 3.90 gear ratio wasn't conducive to towing or freeway cruising with the taller 35-inch tires. Adding the 4.56 gears from Precision brought the final drive ratio within 1 percent of stock and put the speedometer back into check. Switching from the stock rear drum-braking system to the Explorer disc brakes also shortened the truck's 60-to-0-mph stopping distance by 19 feet. The ARB Air Locker works awesomely in the mud, sand, and when we need to climb over obstacles. Overall, this was one of the simplest and most rewarding upgrades we've made to this truck to date. After you've checked out the photos, contact the companies listed in the source box at the end of this article for more information.