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Rebuilding Factory Axles on an M1028 Military Truck

Posted in How To: Transmission Drivetrain on March 20, 2019
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Photographers: Tim McGee

The hunt for the toughest rig possible begins from the ground up. Rugged off-road tires replace tear-happy street rubber, and before long, escalating antics yield a broken axleshaft, hub, ring gear¬, or worse. The upgrade buzzer rings. Catalogs pages ripe with beefed-up parts are torn from their bindings.

Off-roading abuse inevitably takes its toll. However, starting with a rig built tougher from the factory can often cut down on upgrade costs as well as provide a much better platform to begin a build. In our case, the perfect canvas was an M1028 CUCV. A square-body Silverado by any other name, the CUCV was Chevy’s military ride and served honorably in the armed forces for years. Near as we can tell, our unit delivered well over 400,000 miles of hard work before being retired from duty. While in need of a full rebuild to just about every major system (what 400,000-mile truck wouldn’t be?), the truck was the desirable M1028 model. It had all the right hardware boxes checked, including a Dana 60 front axle (ours actually had a limited slip in it, although the clutches were fried), a 14-bolt rear axle with a Detroit Locker, a TH400 transmission, and a 6.2L diesel engine (although that’s only a plus if 165 hp gets your blood pumping).

The truck needed a lot of work because you can’t build a house on sand. The axles were deemed the most reasonable place to start. We pulled them out and stripped them down. With the help of some G2 Axle & Gear 5.38 gears, an Eaton Detroit Locker for the front, and some friends with better tools than we own, we began piecing the axles back together.

The beauty of starting with the right platform is some great hardware from the beginning. Our M1028 military truck came with kingpin Dana 60 and 14-bolt axles from the factory and even had a rear Detroit Locker! However, both axles were worn, battered, abused, and in need of a rebuild.
For help rebuilding our pair of axles, we turned to G2 Axle & Gear and ordered two sets of 5.38 gears, up-rated axleshafts for the front Dana 60, and all of the necessary gaskets and seals to button up each.
PhotosView Slideshow

To begin the rebuild, friend and head mechanic Agapito Arteaga removed the axleshafts and carrier and blasted the axle with a pressure washer.

Next, we hit all of the gasket surfaces with a flap disc to remove any traces of dirt, grime, or old gasket material.
PhotosView Slideshow

GM’s 14-bolt axles employ a drop-out pinion assembly. This was detached from the housing, then the yoke was removed and the pinion pressed out.

Inside the G2 Ring and Pinion Installation Kit is everything needed to install a new set of gears, including gaskets, bearings, seals, and bolts.
PhotosView Slideshow

Our new 14-bolt pinion assembly was mated together with a hydraulic press and reinstalled in the 14-bolt housing.

The 14-bolt has a carrier split, so one covers 3.21 to 4.10 gears and the other covers 4:56 and up gears. Each carrier requires a unique gearset, which we goofed on. A correct carrier was ordered from Summit Racing Equipment, and our factory Detroit Locker swapped right over. If the wrong gearset is installed, the ring-and-pinion won’t align and it’ll be impossible to get a correct pattern on the setup.
The assembled ring gear and carrier were installed in the 14-bolt housing.
Using a dial indicator to measure backlash and gear paint to verify tooth pattern, the G2 gears were set up. GM’s 14-bolt axles use spanner nuts to move the gear side-to-side, which is a pretty easy job compared with pulling bearings and swapping shims.
PhotosView Slideshow

With our 14-bolt rear axle set up, it was time to move on to the Dana 60 front axle. It was treated to the same disassembly and cleaning as the front.

Tim McGee pressed together the pinion assembly and reinstalled it in the cleaned and prepped housing, torqueing the pinion nut to 250 lb-ft.
PhotosView Slideshow

Setting backlash on a Dana 60 axle is a little more difficult than the 14-bolt. Shims are installed behind the carrier bearings that locate it laterally in the housing. Since the bearings are pressed on, that means changing the shims would require pressing the bearings on and off. One way to cheat this is to take your old carrier bearings and grind them just large enough so that they slide onto the carrier. Use these mockup bearings to find the necessary shims required.

Once final measurements are done, we pressed the bearings included in the G2 Ring and Pinion Installation Kit onto the front Eaton Detroit Locker. The locker acts like an open differential off the throttle and locks when you’re on the gas. It’s a great, affordable traction device for those who don’t need the added expense or complexity of an on-demand locker, and it’s brutally strong.
Tooth engagement pattern was verified with marking paint during the assembly process to make sure the ring and pinion were playing nice with each other. You want the gear mesh pattern in the center of the teeth and evenly worn. Depending on your gear mesh you may need to adjust the pinion in or move the carrier left or right. A pattern like the one shown here is the goal.
The finishing touch was to reassemble our kingpins and knuckles (“Some Assembly Required,” Sept. 2018; bit.ly/2BG0h4H) and slide in new G2 axles topped with G2 hubs. The hubs are buttery-smooth, and the completed axles are finally ready to be installed underneath the Army truck.

Sources

Summit Racing
800-230-3030
www.summitracing.com
Eaton
Cleveland, OH 44114
800-386-1911
http://www.eaton.com
G2 Axle & Gear
Compton, CA 90220
310-900-2687
www.g2axle.com

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