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Done In A Day: Jeep Steering Box Swap

Posted in How To: Transmission Drivetrain on August 7, 2018
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You might be at that point in the development of your Jeep build at which a steering upgrade has become the obvious next step. The suspension system that led to the bigger wheels and tires has also led to much more effort needed to get those big meats pointed in the right direction when the trails you’re exploring begin to get into the “black diamond” category. There are a number of options ranging from completely gutting and replacing the steering system with a full hydraulic setup to bracing the factory box so it can handle the twisting and tweaking a bit better.

Of the broad range of options, we’re going to shoot for something in the middle and explore the simple yet effective method of upgrading the steering system on a Jeep Wrangler JK¬–swapping out the factory steering box with a beefed up aftermarket version. It’s a quick and easy job that you can have done in a day in your garage, but the lasting result will be a much better driving experience on- or off-road.

The Big Bore XD (P/N SG688) from Performance Steering Components (PSC) has applications for ’07 to ’18 Jeep JK Wranglers, and that’s what we’re going to focus on here. However, the company also makes a Big Bore XD unit for the TJ/LJ, XJ, and CJ back to ’80. Claimed to be the most powerful (producing 35 percent more turning force than the factory part) and strongest replacement Jeep JK steering box on the market, it is highly recommended for any JK running large tires or a front locker.

Much of the Big Bore XD’s claim to fame is due to the larger piston (80mm as opposed to the factory 70mm); the same as found in late-model Ram 2500/3500 diesel trucks. The gearbox’s sector shaft is also fatter (45mm compared to the factory 35mm). The case (15 pounds heavier than factory) is much sturdier than stock, and all the mounting areas have been beefed up too.

Along with an aftermarket suspension and bigger wheels and tires (this 2012 Jeep JK runs 37-inch tires), comes the need for a steering system upgrade. That’s where the Performance Steering Components (PSC) Big Bore XD steering gear box can make a big difference.

A couple of notes before we go any further: The larger size of the Big Bore XD can create a fitment problem with some aftermarket track bars. It may also have clearance issues that need to be addressed with certain V-8 swaps. Check with PSC about your specific application.

The Big Bore XD steering box is made to operate at pressures as high as 1,800 psi, and PSC recommends the use of its high flow/pressure pump kit (that runs at 1,800 psi and produces 50 percent more volume per revolution than the factory pump) with the Big Bore XD box. However, it is not absolutely necessary, as the factory pump puts out 1,500 psi and will operate the Big Bore XD just fine, just not at the gearbox’s full potential.

The 2012 Jeep Wrangler JKU Rubicon used for this steering gearbox swap rides on 37-inch tires and was built to be a multi-purpose trail runner and off-road camping vehicle, not a hardcore rock crawler, so we determined the Big Bore XD gearbox alone was enough to make a noticeable difference in the performance of this trail runner/daily driver. We now have more than 5,000 miles on the unit and it has solved the “steering moan blues” and instantly brought the steering feel back to factory levels. On the road, the steering is light and responsive, unimpeded by the larger tires. On the trail, the steering remains light to the touch and it takes less fighting with your steering wheel when going over the rough stuff. We have been rewarded with greatly improved steering feel and muscle with the installation of this PSC Big Bore XD steering gearbox.

The PSC Big Bore XD (left) and Jeep JK OE (right) steering gear boxes can easily be compared sitting next to each other. The sector shaft on the Big Bore XD is 45mm; the OE shaft is 35mm. The Big Bore XD delivers a 80mm pump piston; the OE piston is 70mm. Even the case size of the Big Bore XD gearbox is beefier, especially around its mounting areas.
A new pitman arm also came with the PSC Big Bore XD steering gear box. The upgraded pitman arm (left) is not only made to fit the larger sector shaft of the Big-Bore XD, but is a bit thicker all over than the factory pitman.
We began this job by turning the front wheels dead ahead, and then securing the steering wheel in place so that nothing would move during the extrication of the OE box or installation of the PSC Big Boar XD steering gear box.
Next the drag link was loosened from the pitman arm. The anti-sway bar was also unbolted from its frame mount on the driver side, to make access to the nut holding the pitman arm to the steering box sector shaft.
Once the sector shaft nut was removed, a pitman-arm pulling tool was used to loosen the pitman arm from its splined perch on the factory steering box’s sector shaft.
After disconnecting the steering shaft from the gearbox, unhooking the gear fluid lines, and unbolting the box from its mount on the inner side of the frame, the OE steering gear box could be removed.
The Performance Steering Components’ (PSC) Big Bore XD steering box bolted in directly with no modifications to the vehicle. Note the sturdier mounting tang that helps resist twisting. We retained the stock hardware, because that was used to remount the PSC gearbox to the frame.
With the PSC steering gearbox bolted into place, the red lines (marked by PSC during manufacturer) on the steering box and the sector shaft were aligned to make sure the gearbox was at top dead center. Then the steering shaft and hydraulic lines were reinstalled.
The beefy PSC pitman arm was clocked on the splined sector shaft to align perfectly with the drag link ball joint, and then secured with the sector shaft gland nut. After that we reconnected the drag link to the pitman arm.
We wrapped up the job by topping off the steering pump reservoir with fresh ATF to replace what was lost during the steering gearbox swap.


Performance Steering Components
Azle, TX 76020
Duval Offroad Designs

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