In stock form, the Jeep JK Rubicon offers vast improvements over earlier Wranglers. Locking differentials and larger ring-and-pinion gears are two of many benefits found in the Rubicon. So, why would one consider an axle upgrade for an already capable vehicle such as the JK Rubicon? The answer lies in the details.
Yes, the Rubicon offers better axle gears and quality lockers. However, the axle housings that contain those upgrades are still significant weak points and are only slightly better than a mid-'90s Wrangler YJ. We view these flaws simply as a reason to start looking to the aftermarket for a healthy upgrade.
In the old days, swapping a set of street legal Dana 60s into your Wrangler was quite the formidable task. There were plenty of roadblocks to overcome. To name only a few: you had to consider shortening tubes, fabricating control arm and spring brackets, and, of course, regaining a balanced brake system. Thanks to a very limited group of aftermarket companies, the Dana 60 Wrangler has become much more of a reality and much less of a headache. At the front of the pack is Currie Enterprises of Anaheim, California. Currie has been in the axle business longer than any one company and it shows in its latest offering for the Jeep JK. When we say the Currie high-pinion RockJock axles are a direct bolt in, we really mean it in every sense of the word. From the trademark slanted front cover down to the most simple details, like the supplied vent hose extension and sensor wire clamps, the RockJock "package" covers it all.
In addition to the hardware benefits you will see in this article, it should not be forgotten that the Currie RockJock front axle cures a growing problem for lifted Wranglers. There are an increasing number of JK owners who are finding a front driveline vibration problem, which proves near impossible to cure without the addition of manual hubs. Before you offer up the obvious responses like "change your pinion angle" or "check your driveshaft balance," let us point out that on this particular JK, all of the obvious was checked, adjusted, or changed, and checked again. Despite trying multiple driveshafts, yokes, caster settings, etc., this JK could not rid itself of a front driveline vibration when moving faster than 60 mph. It was only after the driveline would be removed that things became smooth and vibration free. The installation of the Currie axle assemblies cured this problem forever, therefore relieving ourselves of the daily shakes on the drive to work. The value of this improvement alone is immense. Follow along as we cover a few of the high points of a typical RockJock axle build.
The JK already had electric...
The JK already had electric lockers and we had become spoiled by their silent and maintenance-free performance. We've used other types of lockers in the past and had very good success. However, the overwhelming benefits of the Eaton E-Locker were impossible to pass up for this project. The E-Locker comes with a complete wiring harness and illuminated rocker switches. Strength is not a concern. The dependability of the Eaton E-Locker is so good that AM General and the U.S. military used them in the H1 Hummer with tremendous success.
If there was ever a reliability...
If there was ever a reliability concern for a particular ring-and-pinion supplier, the brand in question would never find a home in a Currie-built axle assembly. The ring-and-pinion sets from Motive Gear provide consistent setups and no annoying gear noise when installed by one of the experts at Currie Enterprises. The perfect pattern you see in the photo is routine for Motive Gear products and the 5.38 ratio runs as quiet as the original Rubicon 44s.
Rocky trails can deal a rough...
Rocky trails can deal a rough hand to standard Dana 60 differential covers. One nice feature of the canted profile of the RockJock is the lessened exposure for the edges of the cover and the cover bolts. Although the shape of the RockJock center housing eliminates much of this issue, Currie pays special attention to details as simple as reshaping the lower edge of the new cover.
The axle tube flanges on the...
The axle tube flanges on the Currie RockJock are machined from 1 3/8-inch-thick solid steel. A new preinstalled bearing and seal retainer plate makes for a simple axle install once our original backing plates are transferred. The tone wheel shown in the photo is another testament to the engineering design that went into the Currie axles. The JK computer uses wheel speed data inputs to properly control the vehicle Electronic Stability Control (ESC) system. The configuration you see here accommodates the original speed sensors with no negative effects to our onboard computer.
Finding the ideal shock length...
Finding the ideal shock length after a suspension lift is installed often ends with a choice that proves to be close but not perfect. Until you truly cycle your suspension in real world conditions, it is nearly impossible to know your exact compression and extension lengths. Forklifts and ramps help but are used typically for lifting one corner at a time. Shock choices are also somewhat limited to a select choice of lengths and those available may not be ideal for your frame and axle mounts. The repeated adjustability offered by the Currie brackets creates an avenue to get your shocks to be a perfect match to your suspension travel.
One feature that Currie Enterprises...
One feature that Currie Enterprises has accomplished with the front and rear axle is the ability for the RockJocks to be installed into a JK with either mild modifications or highly modified long-arm systems. Control arm and track bar mounts are also drilled with multiple bolt hole choices. These aren't random holes but actually strategic in location so that movement of the top arms can be countered with the bottom arms to maintain overall geometry. This eliminates the need to mix and match bracket extensions and steering geometry "fix-it" kits from other lift kits.
The technicians at Currie...
The technicians at Currie Enterprises have become true experts when it comes to setting up axle gears. This is a shop exercise that goes on every day in the Currie shop.
The stock crossover steering...
The stock crossover steering on the JK represents a monumental step forward from the earlier Jeep TJ. Currie builds upon the benefits of the JK steering system with its custom outer knuckles. The old school Dana 60s found on Ford trucks used a high-maintenance, tapered roller bearing arrangement. The millwork shown on the top outer knuckle is for mounting the steering arm.
Steering arms for the Jeep...
Steering arms for the Jeep JK are visibly different than those found on TJs. The Currie RockJock is fitted with a heavy-duty steering arm. The high mounting point of the new arm provided an excellent drag link angle for the JK.
Mounting a control arm bracket...
Mounting a control arm bracket to a Dana cover may make some people nervous but rest assured, this is no ordinary differential cover. Currie Enterprises has developed this press-formed cover with a thickness of 5/16 inches. The Johnny Joints found on both upper control arm mounts will ensure a quiet ride and excellent articulation.
The quality of the RockJock...
The quality of the RockJock castings is impressive. Note the edge definition of the casting shape in the photo. Every RockJock is fitted with a special protective skid plate made from AR400 plate. AR plate offers excellent abrasion resistance due to a Brinell hardness that is more than double that of carbon steel (400 vs. 175).
Bent tubes and inner C's are...
Bent tubes and inner C's are the Achilles heel of the stock JK front axle. One look at the massive inner C's of the Currie RockJock relieve any strength concerns. The axle tubes used on the RockJock are 3-inch-OD by 5/16-inch-wall.
Currie supplies new 13-inch...
Currie supplies new 13-inch rotors for the front axle. The Currie hub is based on the super strong Ford F-450 unit bearing. Often misconceived, the strength of a unit-bearing hub can be tremendous. Ford has made sure the bearing style of this hub would hold up to the engine weight and GVW rating of the F-450 truck. Currie has taken the strength benefit of this bearing design and added lockout hubs from Mile Marker and an internal tone wheel to suit the JK computer. This is absolutely the best of all worlds for a JK hub.
The RockJock front assembly...
The RockJock front assembly is fitted with a heavy-duty tie rod. Currie uses 1.375-inch-diameter by 0.434-inch chromoly tubing that has been zinc-plated to prevent corrosion.
The final assembly is given...
The final assembly is given one last check before being strapped onto the pallet. The overall width between the rotor faces is 68.75 inches. This is 3.5 inches wider than stock. The width of the RockJock is set by the JK coil spring spacing and the size of the components from which the RockJock is built.
Wheel backspacing is especially...
Wheel backspacing is especially important when using the Currie RockJock. The 17x9 Mickey Thompson Classic II wheels feature 4.5 inches backspacing. Note the clearance between the inside of the tire and the knuckle steering arm. This particular wheel offers the tightest steering arm clearance minimizing the amount of tire exposed past the fender flare.
JKS Manufacturing offers an...
JKS Manufacturing offers an adjustable bumpstop kit to go along with its ACOS coil spring mounts. The combination of these two upgrades allowed the up travel of our axle to be set to the exact stopping point we needed to keep the tires away from the stock fender flares.
Dana 60 axle swaps can be...
Dana 60 axle swaps can be an expensive trial and error adventure for maintaining brake performance. Master cylinder and booster problems often arise when mixing new calipers, proportioning valves, etc. The Currie RockJock eliminates any and all braking hassles by offering the advantage of keeping the Jeep brakes. All four of the JK calipers are used on the RockJocks. Here, the rear backing plates are swapped over from the Dana 44 onto the 35-spline RockJock axle shafts.
Currie Enterprises does offer...
Currie Enterprises does offer rear spring perches with the RockJock. In this case we wanted to try out a set of new spring perches offered by JB Conversions, Inc. The new perches are contoured for the 3-inch axle tube O.D. and feature a bolt-on cap for spring retention.
It is no secret that the stock...
It is no secret that the stock JK driveshafts do not perform well under heavy use. Our Currie axles came with 1310 CV yokes and the new heavy-wall driveshafts from Tom Wood's Custom Driveshafts were set up to be a direct match. One main difference between Tom Wood's driveshafts and others is in the design of the CV components, which are manufactured to Wood's own specifications. Additional clearance is made available by reduced material in some areas while added thickness is found in the higher stressed areas.
Four-door JKs have long rear...
Four-door JKs have long rear drivelines. To sustain tube strength for the rear shaft, Tom Wood's Custom Driveshafts uses a larger tube diameter than that found on the front driveline.