Jeep Wrangler JK Junkyard JK Axle Swap - Part 3Posted in How To: Transmission Drivetrain on June 30, 2014
There are few things better than the payoff of finally getting to wheel once your project is complete. Over the past two issues, we’ve chronicled our junkyard JK axle swap. Using a 2007 Jeep Wrangler Unlimited Rubicon as our test vehicle, we installed a set of used Super Duty 1-ton axles that were originally affixed under a 2002 Ford F-350. While we gave you the breakdown of the high-pinion Dana 60 front and Sterling 10.5-inch rear in previous installments, we still had a few items to take care of to complete the conversion.
Gathered here is the remainder of what we did and how the low-buck 1-ton conversion has panned out in the end.
Dash lights are annoying and our 2007 JK has a few. Not having rear tone rings caused the warning lights you see here to stay illuminated. We used an AEV ProCal module to set the new tire size and gear ratio. This allowed the automatic transmission to shift without issue and our speedometer to read correctly.
To center the front axle, we grabbed an adjustable front track bar from Currie Enterprises. While the crossover steering helps, we went ahead and added a ram-assist kit from PSC Motorsports. The hydro-assist made a tremendous difference in ease of maneuverability on- and off-road.
The Super Duty-sourced high-pinion Dana 60 doesn’t allow for a lot of room on the driver side for a coil bucket. Our tester JK was already affixed with an EVO Manufacturing Double-ThrownDown conversion that fits the Jeep with a King coilover and bypass shock at each corner. Running coilovers will make the front conversion slightly easier, but using a standard coil spring and shock is absolutely possible.
With 14 inches of vertical wheel travel, we needed a driveshaft that could handle the long-cycle suspension. Gone is the stock front driveline, and in its place is a heavy-duty unit from Tom Wood’s Custom Drive Shafts. Wood’s ‘shaft was fit with a 1350 conversion yoke and constant velocity joint at the T-case. A standard 1350 U-joint was placed at the differential.
As is the case with the front, a heavy-duty Tom Wood’s driveline was used out back. The clearcoated driveline was built with a 1350 CV at the T-Case and 1350 U-joint at the axle. We found the Sterling’s differential sits offset to the passenger side just slightly. We were initially concerned that the driveline would make major contact with the JK’s gas tank during travel/articulation, but we haven’t had any issues to date. If your rig is equipped with an aftermarket gas tank skid, be sure to double check for spacing -- It’s going to be close.
If you want a set of blingy mall-crawler wheels, there are plenty of options for the Ford-specific 8-on-170 bolt pattern. Getting a set designed for rugged off-road use is a bit more challenging. We opted for 17-inch Eklipse rims from B.A.D. Wheels. We showed you all about the new-design beadlock wheels in the February 2014 issue (“Beadlock Assist Device”). The DOT-compliant beadlocks make a great fit for this daily-driven Jeep and offer a great balance of performance and strength.
Feeding the JK’s ARB Air Lockers is the company’s dual air compressor. The 100-percent duty cycle compressor mounted easily in the JK’s rear cargo under-floor compartment. ARB also offers a host of attachments and accessories for the 12-volt compressor, which allows you to run some air tools and inflate your rigs tires quickly.
Driving a Jeep, or any rig on 42-inch-tall tires, daily isn’t for everyone, but surprisingly, it’s very manageable in the Unlimited platform. The power from the 3.8L V-6 was pretty lackluster stock. Heavier axles and 42-inch tires did not help the situation. Even with 5.29 gears, highway speeds are possible, but you can forget about overdrive when the hills inch near.
Off-road, the Rubicon’s 4:1 T-case ratio works well as a torque multiplier, but there are definitely times where the JK runs out of steam, especially on long and steep hillclimbs. More gear reduction or moving down to a 40-inch tires would help. Steering the Jeep is extremely easy with the hydro-assist kit. Having the ability to run the ARB Air Lockers open also helps with maneuverability.
The Super Duty brakes are absolutely massive in comparison to the stock setup. That’s the good news. The bad news is that the pedal feels spongy. The brakes work great, but the pedal feel could be better. Bypassing the ABS module might do the trick, but for now, it runs, drives, and stops just fine, so we are leaving it be.
Ultimately, this swap isn’t going to be for everyone, but for the DIY enthusiasts looking to put 1-ton axles under their 2007-2011 JK, it’s hard to beat. The cost of the axles is the biggest draw. The fact you can actually find these axles at your local wrecking yard is another major bonus. If you have the skillset to make it happen at home, then you are saving that much more. Despite the slightly illuminated gauge cluster, we are pleased with the conversion. The confidence and new found durability of our wrecking yard axle swap has been well worth the few minor tradeoffs and then some.
If the tires on the Jeep look big, it’s because they are. Fitting the 42x13.50 Pit Bull Rockers, while not lifting the Jeep to the moon, required a lot of trimming. And we mean a lot. We’ve had great luck with the Rockers in the past, and the 42-inch rubber has worked great with the Jeep’s 116-inch wheelbase.