Deep, suction-like mud has a way of annihilating axle components faster than you can say, “Wow, this mud is really deep!” So, mud-country ’wheelers are starting to turn to 2 ½-ton military axles under their trucks in an effort to bulletproof their vehicles against the inconvenience and aggravation of snapped and pretzeled parts. Many potential buyers turn to Chuck’s Trucks in Orlando, Florida, because Chuck Davis and his crew are some of the leading purveyors of 2 ½-ton military axles.
Chuck’s Trucks has been modifying and installing military axles for 12 years, and the shop offers several packages for the potential buyer. These range from simple cash-‘n’-carry to a full-on install with a custom suspension of your choice. Figure on a base price of about $4,000 for a pair, with disc brakes. Not only that, but Chuck’s offers a couple of braking options for your new Rockwells, including your choice of driveline brakes (for off-road use) or disc brakes (for street use). Both of these systems use Chuck’s Trucks’ custom laser-cut bracketry for mounting the brakes to the axle housing.
Chuck and his crew also can install a Detroit Locker in your new bestest-buddy-in-the-whole-wide-world, and this will ensure that you will not only have a tough driveline, but also one that is totally locked. The upside to installing one of these units is that you get a significantly stout axle that can inherently take a heckuva pounding. One possible downside is that your vehicle has to run at least 44-inch diameter tires. This is because all 2 ½-ton military axles are fitted with 6.72 gears, and as of this moment, there are no aftermarket gears available. But hey, you wanted to fit bigger wheels and tires anyway, didn’t you?
Step By Step
The axles that Chuck’s Trucks uses are procured from military-surplus stock. Some, like this one, are brand spankin’ new, while others have served a tour of duty under 21/2-ton 6x6 military trucks. Over the years, Timken and Rockwell have manufactured these axles, but all of the basic components are generally the same. Parts are plentiful, and interestingly, many parts (such as bearings and seals) are available over the counter from standard parts sources.
To prepare a front axle for modification, the stock drum brakes have to be removed. To accomplish this, the eight bolts that secure the drive cap are removed, as well as the lock-ring and two spindle nuts.
Now the stock brake drum, bearing hub, and outer wheel bearing can be removed. The stock brake drum is discarded. We’ve heard that the drum makes a great planter, but a terrible frisbee.
Once the brake drum is removed, it allows access to the 12 spindle bolts that fasten the backing plate and spindle to the steering knuckle. These bolts are removed, and the backing plate is slid from the spindle.
The spindle and inner bearing are removed from the steering knuckle.
The axleshaft assembly is removed and discarded. Why? Because this side of the diff housing will be cut and narrowed, thus creating a diff that uses the same axleshaft in both sides.
During the many years of 2 1/2-ton axle manufacture, there have been three different kinds of axle joints—Bendix (shown), Rezepa, and U-joint (or Spicer) style. The technicians at Chuck’s Trucks say that testing indicates that all work fine, but the U-joint style is the most desirable, and the most prevalent. It is what they prefer when they’re preparing an axle for use. Owner Chuck Davis says that when the Bendix joint breaks, it releases all of the large bearings, thus creating a large amount of collateral damage to other components.
With the long side of the front axle stripped of its components, a cutting torch is used to remove approximately 7 1/4 inches of the axlehousing. At the same time, the tie rod is shortened to match.
With the axletube cut, you can see how thick the axlehousing is. This is one of the reasons you want one of these heavy-duty monsters.
Stock 2 1/2-ton military axles have approximately 12 degrees of downward pitch engineered into their shape. This helps offset the massive amount of cargo weight the military trucks may carry. When the guys at Chuck’s Trucks re-weld the axlehousing, they remove all but one degree of that pitch. After narrowing, the axle is painted before it receives the customer’s choice of brakes and locker.
Rear military 2 1/2-ton axles are exactly the same as the fronts when it comes to bearings, seals, and centersection. They don’t, however, need to be cut and narrowed like front ones because they were designed for dual tires, and are the perfect width for most 4x4 applications.
One difference between the front and rear axles is that instead of 12 spindle bolts, the rears use 12 rivets. Since the brake assembly is going to be discarded anyway, Chuck’s Trucks simply cuts the unit from the housing with a cutting torch.
To install a locker in a military diff, the centersection must be removed from the housing. This is begun by removing the case bolts. Some of the bolts are accessible with an impact wrench, while some are hidden under a portion of the case, and must be removed with a standard wrench.
After the case bolts are removed, the centersection is lifted free of the housing and placed on a bench.
The centersection is disassembled to gain access to the main spider gears.
Safety wires run through each internal bolt stud to ensure that the bolts retain the torque you give them, and during disassembly these wires are cut so the bolts can be removed. New safety wires must be reinstalled when reassembling the unit.
Chuck’s Trucks can either weld your diff locked, or install a Detroit Locker. The Detroit Locker components are under pressure, so each locker is shipped with a stud and wing nut holding the assembly together. After the unit is installed, the wing nut and stud are removed, and the unit expands to its normal operating position.
Want lock-outs? Chuck’s Trucks has that covered too. The shop offers these massive custom-made Selectro hubs so you don’t have to drive around with the frontend spinning all the time.
If you wish, you can purchase a 2 1/2-ton military axle from Chuck’s Trucks sans brakes. However, Chuck’s Trucks offers two bolt-on braking options. The first is a driveline brake kit, which installs easily using a Chuck’s Trucks custom laser-cut bracket. Driveline brakes are for off-road use only, because using a driveline brake on the street not only is unsafe, but it tends to quickly wear the pinion bearings on the 2 1/2-ton axles. For slow trail travel however, the kit works great, and it uses a standard over-the-counter rotor and caliper.
To complete the 2 1/2-ton Rockwell install, Chuck’s Trucks likes to use a divorced NP200 transfer case. The unit is installed in a custom-designed carrier to position the ’case for minimum driveline angles. The entire system bolts on to a stock or modified frame, and Chuck is working on a new electronic actuating system for operation.
The finished install is clean and functional, and can include a Detroit Locker, disc brakes, and a leaf spring or coil suspension. The axles allow fitment of standard 15-inch-diameter wheels with up to 4 1/2-inches of backspacing and a width of 14 to 20 inches.