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2007 Jeep Wrangler Rubicon Axles - Project 'Con Artist

Posted in Project Vehicles on October 1, 2007
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Photographers: Ken Brubaker

We took delivery of our 2007 Jeep Wrangler Rubicon Unlimited project what seems like an eternity ago, and we have been busily building it up ever since. As with all Rubicon JKs, our manual-transmission, four-door arrived from the factory with 4.10 gears, and with plans for 35-inch rubber, we knew we were going to need extra axle beef and lower gears.

For Project 'Con Artist, we turned to one of the highest quality manufacturers of drivetrain components, Superior Axle and Gear out of Rancho Cucamonga, California. With its own forge in East Los Angeles, Superior can still offer the "Made in the USA" tag on many of its products. Superior is also known for its innovation and was not only the first company on scene with aftermarket gears for the JK's Dana 44 axles, but also the first to offer chromoly axleshafts for the JK. We were privileged enough to get our hands on the very first Super JK-R production chromoly axle kit and one of the first sets of 4.88s (5.13s are also offered) off of the production line.

The Superior Axle & Gear Super JK-R kit could be the next big thing in JK axle upgrades and contains equal-length rear 35-spline chromoly axleshafts, a rear ARB Air Locker, and front 32-spline chromoly shafts in addition to all of the bearings, seals, studs, and hardware needed for installation. What this means is the rear axles are upgraded from 32 splines and the front axles are upgraded from 30 splines. The factory rear 32-spline locker moves to the front axle as a new ARB Air Locker is provided for the rear. The benefits are many, including stronger axles at a lower price since only one new locker is needed for the upgrade. Also, the Rubicon's stock unequal-length axleshafts are replaced with the new equal-length shafts. Lastly, the ARB Air Locker can be wired in to the stock harness, making for seamless integration and factorylike operation.

Superior's chromoly axles are serious pieces of off-road hardware, made in a single-piece forging, which provides an excellent grain structure for greater strength. These axles are CNC-machined to exacting specifications, which include rolling the splines for a 35 percent increase in spline strength, which help the spline to resist twisting and premature wear. Next, the axles are CNC induction hardened in-house, giving the axles their awesome overall strength. Superior uses scanners to ensure proper depth penetration of the heat-treating. Lastly, the axles are coated in black oxide, in a seven-tank process, to resist corrosion.

And don't forget the gears, which are the only gears on the market to have a dual bolt pattern designed to work with one of two possible bolt sizes (midway through the 2007 production, Jeep upped the ring bolts from 7/16-inch to 1/2-inch to accommodate overseas diesel models). Even the installation kit comes complete with both sets of bolts, so no matter what setup you have, you are covered.

1. The 35-spline rear Superior shaft is on the left; the 32-spline rear factory JK Rubicon shaft is on the right.

Superior will also offer a rear-only kit for those Rubicon owners who have their own plans for the front axle, and just in case you forgot to order your Sahara with a locker, once again Superior has your back with the rear Super JK axle kit that will work with non-Rubicon models. There will also be direct replacement axles available down the line.

For the install, we visited our friend Mel Wade at his shop, Off Road Evolution in Fullerton, California-one of the fastest growing and most respected shops in the Southern California area. Mel and his capable staff can handle a wide variety of needs ranging from lift-kit installations to full custom fabrication and you won't find a nicer group of people to do business with.

PhotosView Slideshow

5. When you are on the trail, you want equal length axleshafts, so if one breaks you only need to carry one spare to fit either side. Guess which set of shafts pictured here is offered on the "Trail Rated" Rubicon. If you guessed "right" you would be wrong-all Rubicons have unequal rear shafts, while non-Rubicon models have equal length. The Superior Super JK will upgrade your rig to proper equal-length shafts.

PhotosView Slideshow

After doing the calculations, we decided on the 4.88 gears to complement our 35s, knowing that the extra leverage over a 4.56 would be needed for the stock 3.8L to move the heavy Jeep, especially after increasing the rotating mass and decreasing the aerodynamics. After 5,000 miles, we couldn't be happier with our selection. With the six-speed manual, our JK cruises just above 70 mph at 3,000 rpm, still pulls in a hair over 16 mpg (if we really behave), and has gotten us all over Moab with us never wondering once if we should have gone for a different ratio. In fact, we think this is a perfect combination of streetability, trailability, and every day comfort. Next up, we'll have to figure out how to get our lockers to operate in anything other than 4-Lo.


Huntington Beach, CA 92647
Superior Axle & Gear
Rancho Cucamonga, CA 91730
Off Road Evolution
Fullerton, CA 92833

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