Lockers are mandatory front and rear for all vehicles that go on the Ultimate Adventure. But with all the street miles we have to tackle just getting to the trail, it's nice to be able to run open from time to time. The selectable ARB Air Locker has proven itself in past Ultimate Adventure truck buildups, so when we chose the Pro-Rock front axle for our K-10, we knew what locker would find its way inside. The gear techs at Dynatrac bolted our ARB in with a Motive Gear 5.13 high-pinion gearset and set a textbook pattern.
With the axleshafts, eight-lug Dynatrac wheel hubs, and brake kit installed, all we had to do was sling the front Pro-Rock axle under our truck. We've done this with three floor jacks and a few sore backs in the past, but the crew at GM Truck Center made it so much easier with a little help from a forklift. To make our installation super smooth we ordered Dynatrac's spring plate and U-bolt kit so we wouldn't have to track down these parts in a junkyard.
Since we were only planning to run a 4-inch Tuff Country suspension lift on the front of our truck, we knew we were going to have to make room for our crossover steering system. The rivets were air chiseled out of the original engine crossmember and then we had to cut it in half to remove it from between the framerails.
We bolted in this high-clearance crossmember from Missouri Off Road Outfitters that ties the two engine mounts together and leaves a lot more room for a drag link. Since we had the whole front clip off the truck anyway, we added Off Road Design's steering-box brace to triangulate the box to the front crossmember.
The rear 14-bolt axle for our UA K10 started life in a '78 GMC van. After we pulled it out of the junkyard we took it to Off Road Unlimited to have it rebuilt. First the housing was chemically stripped and the original spring pads were cut off. The pinion support was cleaned and the inside of the housing was painted and prepped for the all-new 14-bolt ARB Air Locker and a Motive Gear 5.13:1 ring-and-pinion.
Off Road Unlimited did a world-class job on the rear axle. The attention to detail would make some heart surgeons look sloppy. The inside of the housing was painted to facilitate oil drain-back and help seal the casting. The pinion support was then assembled with a new bearing and a 1410 yoke modified by ORU to use U-bolts instead of straps.
When ordering 5.13 gears for a 14-bolt axle with an ARB, make sure to specify a thick ring gear, as the ARB carrier is designed to use gears for the 4.10-and-down case. If you're familiar with ARB differentials, you'll notice the locking mechanism has been moved to the opposite side of the carrier to make room for the third pinion bearing in the 14-bolt design. When routing the air line, ORU makes sure that it doesn't rub against any internal surfaces.
Rebuilding the 13-inch drum brakes on a 1-ton axle is expensive, not to mention they weigh a ton. When it comes to shopping for disc-brake conversions for these axles, the most complete package on the market comes from Off Road Unlimited. Sure, some people can piece together a bracket and a caliper combo at home, but ORU goes beyond that and includes a rotor, new wheel studs, a brake-line kit, a master cylinder, and an application-specific proportioning valve.