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2.5 Ton Rockwell Axle ARB Locker - Air Locking Rockwells

Posted in How To: Transmission Drivetrain on January 1, 2009
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It doesn't get much tougher than the 2 1/2-ton Rockwell axle. Used by the U.S. military for decades, these massive top loaders have continued to gain popularity in the off-road market, mostly due to their relatively cheap price. They are especially appealing for guys looking to run 44-inch-plus tires where weight is not really a concern. Responding to the increasing fame of this axle, ARB has stepped onto the scene with an all-new Air Locker designed as a full carrier replacement for the 16-spline 2 1/2-ton Rockwell axle.

As the first selectable locker to hit the market for these robust axles, the unit is intended to improve both trail and street characteristics over traditional full-time lockers. And given the fact that Rockwells are not factory-equipped with selectable hubs, dropping in a selectable locker is an easy way to improve your rig's steering and reduce wear on parts.

With the exclusive on the 2 1/2-ton locker and eager to put it in, we enlisted the help of Randy's Off Road in Azusa, California, so that we could rip into the roughly 700-pound axle with someone with a bit of big diff experience. It didn't hurt that he has a forklift to move the backbreaking axle!

The good news about wrenching on a Rockwell axle is that they are simple and you don't need to have a special engineering degree to rip one apart. The bad news is everything is very heavy and we must insist that you use an engine hoist, winch, or some sort of mechanical lifting device so that you won't write us angry letters about herniated discs and crushed toes! Even with the 6.72 gear ratio and massive size, we think there is much that can be done with these axles, and the aftermarket just seems to be warming up. Be sure to stay tuned. We plan to dive into the 2 1/2-ton realm with a little (big) project of our own.

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Rockwell Third Member Basics
The 2 1/2-ton third members utilize a gear-reduction configuration that rotates power through a 2.44:1 ratio upper ring-and-pinion down to the 12-tooth intermediate gear and massive 33-tooth bull gear (2.75:1 ratio). This series creates an end ratio of 6.72. Weighing more than most complete 1/2-ton axles, the centersection raises roughly 9 1/2 inches above the axletube and has the ability to be turned 180 degrees, giving you the option of running either a driver- or passenger-side drop configuration.

Our test truck had modified the Rockwell axles with a high-clearance differential skid and an off-road-only pinion-brake setup. With the 2 1/2-ton axles still sporting the factory hubs, shafts, and six-lug bolt pattern, we plan on thoroughly testing the Air Locker over the next few months. We'll be taking driver impressions as the 49-inch Iroks are sure to put the components to the test. For more about how the ARB Air Locker performed, cruise over to our website at



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