It’s a complete natural, right? Our event is called Ultimate Adventure. Dana’s signature line of crate axles is called Ultimate Dana 60s. It’s like peanut butter and chocolate: How could we go wrong putting the two together? Especially given the fact that Dana’s first variant of its crate axle program caters to the JK Wrangler crowd with the correct width, pinion angles, and ABS, steering, and bracket systems installed to make these axle assemblies completely ready to bolt in. Builder versions with no brackets or Cs installed and with your choice of kingpin or ball joint knuckles are coming, but we think hitting the super-hot JK market first was a wise move.
We’ve been in the loop with Dana as it developed these crate axles for roughly the past 10 years, lending advice when asked and patiently waiting for the final result of many, many brainstorming meetings. But even after we suffered for almost a decade of anticipation, when they finally hit the scene there was no anticlimactic let down. These bolt-in JK axle assemblies are flat-out awesome. For starters, the front axle is a high-clearance, high-pinion design with a nodular iron diff cover. The ball-joint knuckles swing on large inner Cs that allow massive Spicer SPL-70 axleshaft U-joints. These are huge 1550-series sized U-joints that dwarf regular Dana 60-sized axle joints. The SPL-70s are housed in 35-spline 4340 nickel chromoly inner and outer axleshafts. High-quality 35-spline Warn locking hubs and a dead splindle hub design (not unitbearings) are outboard the massive Ram 2500–sized rotor and caliper package with ABS connections ready to plug in. The good stuff continues to the housing, with a ribbed centersection that helps prevent the bottom of the diff from getting hung up on rocks, super-strong 0.370-wall, 3.5-inch-diameter axletubes, and your choice of 3.73, 4.10, 4.88, or 5.38 gears with a 10-inch ring gear diameter and an Eaton ELocker or ARB Air Locker diff. And naturally, all the brackets are heavy-duty and welded in place ready to accept all your current JK linkages, and there’s a high-mount steering arm already installed on the passenger-side knuckle for lifted applications.
The rear axle is similar in many respects to the front, with heavy-duty brackets, plug-and-play ABS system, massive brake rotors and calipers, and full-floating 35-spline 4340 nickel chromoly axleshafts. Like the front, the rear features a 1350 driveshaft yoke and ribbed centersection with nodular iron diff cover. However, the rear axle features slightly thicker 0.390-wall, 3.5-inch-diameter axletubes and is a low-pinion design for additional strength. The rear runs the standard Dana 60-sized 9¾-inch ring gear but shares the same locker and gearing options as the front axle.
With Dana on board as Official Crate Axle of Ultimate Adventure, we happily ordered a pair of Ultimate Dana 60 crate axles with 4.88 gears and Eaton ELockers for our Cummins-powered build. Two large crates with “Genuine Dana Crate Axle” arrived and Tech Editor Verne Simons wasted no time in making the UACJ-6D chassis into a roller. After unboxing the Skyjacker LeDuc Series coilover suspension, shortening the JK Unlimited frame roughly 9 inches between the wheels, and setting the frame up on jackstands, Verne roughed on the Skyjacker control arms and swung the Ultimate Dana 60 axles underneath. A Yeti XD Series JK tie rod and drag link system from Steer Smarts here and a triple-master cylinder brake system from Wilwood there, and the UACJ-6D was ready for the next phase of the build, which we’ll show you next time.
Since the local FedEx guy isn’t gonna drop several hundred pounds of axle off at your doorstep, Verne arranged to have our UD60 crate axles shipped to Rob Bonney Fabrication, where a forklift could transfer them onto Verne’s trailer. Once back at Verne’s, we popped them open and swung them onto the shop floor with an engine hoist.
The front Ultimate Dana 60 houses a reverse-rotation ring and pinion, commonly referred to as a “high pinion” design. In a front-drive application, this is stronger since the front driveshaft spins in the opposite direction as the rear. A standard-rotation, low-pinion front axle runs on the coast side of the gearset and can result in chipped ring gear or pinion teeth under harsh wheeling. A reverse-rotation, high-pinion front runs on the drive side of the gears, allowing full mesh under load and much higher survivability.
The brackets are really heavy-duty with most at least ¼-inch thick or better. All the brackets are welded in the factory positions to allow a slam-dunk retrofit in your JK Wrangler.
The driver-side upper control arm mount is cast into the centersection, while the passenger-side mount is ¼-inch-thick steel. Both come loaded with OE-quality rubber bushings. Since we are running an Eaton ELocker, our locker’s electrical plug was already installed and ready to hook up to the locker wiring harness.
There are a few minor considerations if retrofitting these in a regular JK. First, the centersections are roughly 1 to 2 inches taller than a JK Dana 30 or Dana 44 by virtue of the massive ring gear and beefy housing, so a small lift or lowered bumpstops might be required for a stock vehicle. Also, the pinions are roughly 1 to 2 inches longer than stock JK axles and feature big 1350-series driveshaft U-joints. And finally, the wheel bolt pattern is 8-on-6½ rather than the JK-specific 5-on-5, so you’ll definitely need new wheels. We’d suggest going with a 17-inch-diameter wheel to clear the brakes.
Verne’s shop puppy approves of the finished rear install. Granted, we’re using coilovers in lieu of the factory separate coil and shock arrangement, but otherwise the Ultimate Dana 60 rear plunked right in place with the Skyjacker adjustable rear track bar (PN JKFTBA717) and adjustable control arms.
Up front, the Steer Smarts Yeti XD tie rod fit like a dream, but we failed to consider the high-mount steering arm that comes on the Ultimate Dana 60 when we ordered the company’s Yeti XD high-steer drag link. After realizing our goof, we swapped out the drag link end for a Yeti XD undermount version to get the drag link off the frame at full bump. The Steer Smarts components are 1½-ton-rated with 0.250-wall tubing and solid chromoly forged ends. In our opinion, they’re simply the finest JK steering linkages we’ve come across.
Here’s a shot of the undermount Yeti XD steering arm after many months of hard trail use, a few rainstorms and deep water crossings, and a severe alkali mud bath. Also note the massive size of the long-life, sealed Spicer SPL-70 U-joint and clipped ABS wire since Editor Hazel has no plans of adding ABS to the UACJ-6D at any time.
It’s getting closer. With the front axle slung under the Jeep, Verne installed the Skyjacker air bumps and set finished compression height by welding a taller landing pad onto the coil mounts. The Skyjacker front drag link allowed the front axle to be centered under the vehicle. Verne also adjusted the Skyjacker control arms to dial in roughly 6 degrees of positive caster.
Editor Hazel was insistent on running a Wilwood triple-master cylinder setup like he uses in his 1953 DJ-3A flatfender. Available with either swinging or hanging pedals and forward- or reverse-mount master, the UACJ-6D has plenty of firewall real estate to run the hanging pedals, so we went with Wilwood’s PN 340-15072 forward-mount pedal assembly. Verne mocked the pedal assembly in place before building a strong reinforcement plate to prevent firewall flex on hard braking.
The triple-master setup confuses some people, but the two inboard masters feature a 7/8-inch cylinder bore and run the front and rear brake circuits separately. Brake bias can be set by adjusting the balance bar on the pedal assembly. The outer ¾-inch-bore master actuates the clutch slave cylinder, which in our case is a Wilwood pull-type (PN 260-1333). Verne plumbed the lines before bleeding the masters and then hooking up the system.
While staring at a huge hole where the factory floorboards used to be, Verne’s creative brain got to work, and he decided to use the crates that housed the Ultimate Dana 60s and Cummins R2.8 Turbo Diesel crate engine as the UACJ-6D floor. Awesome!
The final tweak was mounting the Wilwood pedal pads, which feature 15 mounting holes to allow a decent amount of adjustment depending on how your feet fit your chassis. As a bonus, the empty holes allow a huge amount of grip when stepping on the pedals.