When it comes to building a trail rig, pairing the right axles to the vehicle is incredibly important. While tire size is generally the first thing to come to mind when matching the right axle assembly to a given vehicle, there’s quite a bit more to think about. Axle width, available aftermarket parts, vehicle weight, and, of course, your powerplant are all major parts of the equation. With plenty of aftermarket axle manufacturers offering bolt-in heavy-duty axle assemblies these days, upgrading your 4x4 has never been easier.
However, if your vehicle doesn’t have great aftermarket support, or you don’t have the coin to go all-in on a fresh set of axles, then you’ll likely find yourself on the same parts journey we embarked on. With plans of running 40-inch-tall tires, and not looking to compromise on strength, we sought out two of the most coveted used axles on the market—a high-pinion Dana 60 front and a GM 14-bolt rear. Pound for pound, both are exceptionally strong and can handle big tires and serious horsepower with very little upgrades. Even better? If you’re a savvy searcher, you can pick up both for less than a grand.
Our high-pinion Dana 60 front axle was pulled from an ’02 Ford F-250. It’s a ball joint–style axle that uses unit bearings and is a little over 69 inches wide. The name high-pinion simply means the pinon sits above the centerline of the axletube. The two main advantages of this design are that the pinion powers on the stronger drive side of the ring gear and the higher placement equates to a driveline that is tucked farther out of harm’s way.
Part of the attraction of the 14-bolt is the fact that it’s a commonly used GM rear axle that’s been around since 1973. Given that most 14-bolts are full-float axles, it removes the load from the axleshafts and transfers it to the hub. This allows for a stronger axleshaft and increased load-carrying capacity compared to a semi-float axle. Add that to the fact that the 10.5-inch ring gear is extraordinarily strong, and you have yourself an axle that can easily handle up to 44-inch-tall tires in stock form. A high-pinion Dana 60, however, is a bit tougher to find.
Unlike the 14-bolt, there are many variants of the Dana 60. We ultimately decided to narrow our search to the Dana 60 found under the front of ’99-to-’04 Ford Super Duty trucks. These high-pinion axles have excellent aftermarket support, the required driver-side drop for our project, and are much easier to find when compared to the older kingpin-era high-pinion Dana 60s. However, it’s not without faults and challenges.
Once we finally had our axles, we dragged them to the off-road experts at Low Range 4x4 in Wilmington, North Carolina. It would be here where we would completely dismantle and rebuild both axle assemblies. Follow along as we cover the pros and cons of both of these junkyard 1-tons and transform them into a formidable axle set.
The ’99-to-’04 Ford Super Duty trucks have the leaf-spring perch cast into the differential on the driver side of the axle. This makes it a little challenging when modifying the axle to accommodate a link suspension. Thankfully, there are axle truss kits and brackets offered specifically for this axle. This is something we’ll address when we move to the suspension leg of our build.
The GM 14-bolt we picked up is a late-model unit, which means it came with disc brakes and a 68-inch WMS. With a max torque rating of 6,242 pounds, it’s by far the best bang-for-your-buck full-float axle you can find in a junkyard. While earlier models have the same 10.5-inch ring gear, most will be equipped with drum brakes and a narrower 65-inch width. Though converting to disc brakes is easy, the narrow width can be a challenge, depending on the application it’s being placed under.
Since we’re planning on a custom multilink suspension for our truck, all of the stock axle brackets needed to be removed. Low Range 4x4 owner Kelly Carter used a plasma cutter to remove the majority of the unneeded material and then spent some time with a grinder to get the axletubes smooth throughout.
Part of what makes the 14-bolt so strong is the pinion design. Unlike most conventional differentials, the 14-bolt pinion housing is bolted to the axle assembly. This 30-spline, 1 3/4-inch pinion also has the benefit of an internal support bearing that ensures the pinion can’t deflect.
Replacing the open differential carrier on our 14-bolt is an ARB Air Locker. While we’re saving a little coin by reusing the 14-bolt’s stock 30-spline axleshafts, for those looking for even more strength, ARB now offers 35- and 40-spline versions of its legendary selectable locker.
Paired with the ARB differential is a set of all-new bearings and 5.38 gears from Nitro Gear & Axle. Given the truck these axles will go under has a modest powerplant, the numerically high ratio is needed to turn the 40-inch treads easier on- and off-road.
Since our 14-bolt came from the factory with disc brakes, we just swapped the old parts out for new to make sure we were starting fresh. This axle will also make it much easier to adapt a parking brake, which is something that should never be overlooked.
While a matching 5.38:1 front gear ratio was a no-brainier, this isn’t an ordinary Dana 60 gearset. Nitro Gear & Axle has created an all-new 10-inch-diameter ring gear for the reverse-rotation Dana 60. This thick gear is shot-peened for added strength and fits inside the diff without any modification. While moving up 1/4 inch in gear size might not seem like a big deal, it gives you Super 60 ring-and-pinon strength, without the hassle of moving up to a 10-lug front axle.
Since this rig will see just as much on-road time and it does off, we wanted to make sure we fit it with a selectable locker set. With the flip of a switch, the compressed air transforms the ARB Air Locker from a completely open differential to a fully locked one in seconds. This reduces wear on our driveline components and equates to a more versatile 4x4.
Both of our ARB Air Lockers utilize a two-piece case with forged internals. These carrier-replacement differentials are also significantly stronger than the original cast-iron open diffs. Both traction aids will require an external air source and a small hole in the differential housing for the air line to be plumbed through.
The ’99-to-’04 Super Duty Dana 60 comes stock with 1.5-inch-diameter axleshafts and massive 5-806 U-joints. Given that we’re planning on serious wheeling adventures, we swapped out the stock axleshafts for a set of 4340 chromoly ’shafts from Nitro Gear & Axle. This axle kit also increased our outer stub shafts from 30- to 35-spline.
Moving up to a larger 35-spline stub shaft meant we would need to have our unit bearings modified for the larger axle. We had ours machined large enough for a spindle bearing to be pressed in to add support to the shaft.
Unlike a unit bearing that you might find on a Jeep Wrangler JK, this style of Dana 60 unit bearing works with a lock out–style hub. This allows the front axleshafts to be unlocked versus constantly engaged like the Wrangler. Since we moved up to a 35-spline outer, we upgraded from our OE hubs to a much stronger set from Warn. These Premium Series hubs have an all-metal construction and dual seals to make sure locking in (and out) is easy time and time again.
Aside from pressing in new ball joints on the axle, we swapped the passenger-side steering knuckle out for one from Ujoint Offroad. Since the 4x4 van conversion specialist frequently use the ball joint–style axle on its builds, the company had a high-steer knuckle made. This setup uses a high-steer arm that attaches to the knuckle via five Grade 8 bolts. Given it’s already tapered for an above-mount 1-ton tie-rod end, all we’ll need to do is build a set of steering links and bolt the joints in place.
For those of you familiar with these two axles, you may know that the 14-bolt has an 8-on-6.5 wheel bolt pattern, while the Super Duty–sourced 60 has an 8-on-170 pattern. To match the separate patterns, we had the machine shop re-drill our unit bearings with an 8-on-6.5 pattern. The only part left was to drill out the stock brake rotors with the new standard wheel bolt pattern.
Stock diff covers are typically thinner-gauge steel to help with cooling. The downside of this is they don’t offer much in the way of rock protection. We found a happy medium by shielding both diffs with Nitro’s X-treme series covers. These reinforced aluminum covers not only provide increased protection over the stock units, but they also help to dissipate heat thanks to the finned design. There’s even a drain, fill, and overflow port to make servicing the diffs much easier.
For now, our axles are complete. Yes, they still need suspension brackets, and the rear needs hard brake lines routed, but that will come once we finalize our suspension plans.
If you’re curious where these junkyard jewels will end up, then wonder no more. Pictured here is maybe one of the most underrated build platforms of its time. It’s an ’01 Chevy S-10 4x4. While most S-10 platforms are a dime a dozen, the four-door versions are slightly tougher to find. This one is fit with one of the General’s most reliable engines—the 4.3L V-6, which is backed by a 4L60E. We love the body-on-frame construction and crazy cheap replacement parts; in many cases, its cost is far less than a used Tacoma Double Cab!
The idea here is to build a heavy-duty trail rig that we can easily tote our family along in. We’ll be the first to admit that these trucks don’t have great aftermarket support. However, that doesn’t mean you can’t adapt parts made for other pickups for this one. Next up on the docket—suspension.