A few years ago, if your Wrangler was running on 35s, you were playing in the big league. Now 37-inch rubber has almost become the norm on the street, while the serious trail-running crowd is spinning 40s. Changes in gearing can give your rig the performance to cover some pretty serious terrain on those big tires. However, there’s another area JK owners soon discover that also needs addressing when rolling on rubber that’s hip-high: the power steering. The bigger the tires, the more steering muscle it takes to turn them; especially when the going gets slow, the terrain gets steep and boulder strewn, or the mud is thick and the ruts deep.
Turning Big Rubber
To offset the strain big tires bring, Texas-based Performance Steering Components (PSC) has used its vast motorsports expertise to design hydraulic steering-assist kits specifically for JKs running big tires. The hydro-assist system is said to give a 50 percent boost in turning muscle to the stock Jeep system, all without changing the steering effort and feel from the driver’s seat.
PSC’s hydraulic steering-assist kits are well designed, and have all the parts needed for a clean, custom-looking installation. For the most part it’s a bolt-in kit, with the only welding needed on the tabs for the track bar bracket so the hydraulic cylinder’s ram can be attached to the drag link.
Jeff Allen, one of the co-owners of PSC, says their kits target three key components in the later-model stock JK steering system for modification or replacement: the steering gearbox, the power steering pump, and the PS reservoir.
PSC's new steering gearbox is a modified unit that provides two extra pressure ports to allow use of a steering cylinder on the front axle. The steering gear modifications include replacement of the spool valve housing and the modifications of the spool valve to accelerate the fluid through the gear as fast and unrestricted as possible. Jeff told us, “These modifications are critical to the overall speed and operating temperature of the system.”
That’s also why PSC replaces the OE power steering pump with a new one that increases the amount of fluid driven to the gearbox by 50 percent per revolution. This is the key to producing more fluid power at lower engine rpm, which is critical when wheeling in demanding conditions. Jeff says the system pressure is also increased from the stock pump’s 1,500 psi to 1,750-1,800 psi, again to facilitate the rapid delivery of fluid to the PSC steering-assist cylinder and the muscle needed to handle big tires.
Handling Heat & Aeration
Increasing fluid pressures and volume creates more heat in cylinder-assist steering systems, which is why PSC highly recommends the use of both a cooler and quality power steering fluid. “We recommend Swepco 715 in our systems because we think it’s the best power steering fluid on the market,” says Jeff. “Swepco has a anti-foaming agent that actually improves as more heat is created in the system.”
Keeping the power steering fluid from aerating aids the pump in the fluid delivery to the gearbox and on to the hydraulic cylinder, which is why PSC includes a custom aluminum P/S reservoir with internal filter that replaces the plastic OEM reservoir. The PSC reservoir holds more fluid, and its design provides special baffling to prevent aeration, which in turn prevents P/S pump cavitation.
PSC’s SK276 Cylinder Assist Kit is designed to keep the stock steering feel while boosting the tire-turning force by as much as 50 percent. The kit includes a new steering gearbox modified to provide fluid to the steering ram, new power steering pump, and PSC remote reservoir along with hoses and hardware.
PSC has also found that in the 2012-and-newer JKs, the pressure hose from the pump to the steering box has a restrictive Teflon lining that has been known to melt and break free under extreme conditions. This material then travels into the pressure-side port of the gearbox, causing the system to overheat; and in some cases, causes the steering system to lock up, according to Jeff. (The Teflon liner was only installed to reduce power steering noise in the OE system.) PSC fixed this issue in the cylinder-assist kit by including a new pressure hose that doesn’t have the Teflon lining.
We worked with Dunks Performance to install a PSC four-door JK Cylinder Assist Kit (P/N PSC-SK276) on a 2014 Wrangler Unlimited Rubicon running Nitto 40s hanging off a Dana Ultimate 60. (PSC makes a similar kit for D44s.) The stock power steering system had met its match trying to turn the big tires on several difficult off-road outings. Future runs over big rocks, deep ruts, and soft sand will be a piece of cake—and with no change to our JK’s highway manners.
Our installation began with the removal of the air intake tube, air box, and fan belt, which then allowed tech Casey Castle easy access to the JK’s power steering pump that is also pulled out. An open-end 18mm wrench handles the pressure line to the pump, and a 13mm socket takes care of the pump’s mounting bolts.
PSC provides a new P/S pump assembly and mounting bracket with the kit. The pump has been modified to deliver higher volume at lower rpm than the OE pump, and bumps the fluid pressure up from 1,500 psi to between 1,750-1,800 psi.
Casey used a few drops of thread locker on both the pump-to-bracket mounting bolts and the bracket-to-engine block bolts to ensure they’ll stay torqued at the factory specs. The factory power steering lines were then reinstalled on the new pump assembly.
We used a razor knife to cut the hose feeding the OE reservoir. Cut as close to the reservoir as you can so the new fitting and hose extension can be installed in the old hose.
The PSC kit replaces the plastic OE P/S reservoir with a higher-capacity aluminum one that has special baffles to prevent aeration, along with a filter. Installation requires freeing the wiring loom; it can be adjusted to give more space around the headlight for the new reservoir.
The special bracket to mount the PSC reservoir in the same location as the OE reservoir required grinding a small relief to better match the bodywork by the headlight of our JK and elongate the mounting bolt hole. These little modifications allowed us to slide the PSC reservoir about a 1/2-inch toward the driver’s side from where it would normally be mounted. Otherwise the filler cap on ours would have been under the edge of the radiator cap.
Along with the new reservoir are new fittings and hoses that had to be connected to the factory hard lines. The fittings are the low-pressure, push-on-type, which made this part easy. The larger (top) fitting took a 1 1/4-inch wrench, and the smaller one a 7/8-inch to snug tight.
Note the close proximity of the PSC reservoir to the radiator filler cap. If the mounting bracket hadn’t been modified to move the reservoir toward the right headlight, it’d be very difficult to remove the PSC cap to add/check fluid, or replace the filter inside the new reservoir.
After making sure the steering wheel was straight, we unbolted the steering shaft coupler and then slid it off the steering box. We had also removed the power steering lines from the top of the gearbox.
All that held the steering box to the frame were these four 18mm bolts, which made swapping out the OE unit with the modified PSC one fairly straightforward.
Casey used a puller to remove the pitman arm prior to maneuvering the steering gear out of the JK. The arm was later reinstalled on the PSC box.
We found that it’s a really good idea to replace the O-rings on the old power steering high-pressure lines with new ones. If you don’t, the odds increase of having an oil leak before you head down the road.
When laid side by side, it’s easy to see the modification to the PSC gearbox (left), which has a spool valve housing with two additional ports that control the high-pressure fluid delivery to the steering-assist cylinder. What you don’t see is the spool valve has been modified to get fluid to the assist-cylinder as fast and as unrestricted as possible.
The new PSC steering box was reinstalled using the original mounting bolts, then the steering shaft coupler was bolted on, the pitman arm reinstalled, and the OE feed lines (with new O-rings) from the P/S pump reattached. New hydraulic lines that came with the kit for the assist-cylinder would be installed next.
Jp Pro Tip: When building the high-pressure hoses that come with the kit, remember the sleeve threads on counter-clockwise, while the male insert goes in clockwise. It also goes smoother if you dab a little white lithium grease on both the sleeve and the insert threads
Here’s how our fittings looked after they were installed in the PSC steering gearbox. The other end of each hose runs down to the steering-assist cylinder that pushes/pulls the drag link.
PSC includes a 1 3/8-inch Easy Tie Rod Clamp to connect the cylinder’s ram to the OE drag link, or in our case, a Synergy replacement, which is what our trail-ready JK had already been equipped with. Clamps for larger drag links are an option. The clamp is left loose until the assist-cylinder mounting is finalized.
After Casey placed the triangular-shaped mounting tabs on the fixed end of the steering-assist cylinder, he positioned them so they’d be located tight against the track bar mounting bolt before they were tack-welded into place.
It took just a minute for Casey to run beads along both sides of the cylinder mounting tabs, which were then painted to keep rust at bay and to make the finished installation look clean.
After the tabs were in place, we attached the fixed end of the cylinder to them, tightened the drag-link clamp, and attached the steering-assist ram; then we finished the installation of the hoses running from the modified steering gearbox to the cylinder.
Filling the PSC reservoir with Swepco 715 Power Steering fluid (per PSC’s recommendation) and bleeding the system were the last steps in our quest to add more tire-turning muscle to our JK’s power steering system.
Jp Pro Tip: If you are running a Synergy 8002 Tie Rod, hydro-assist will accentuate any vertical flop. The remedy: Replace the Synergy tie-rod boots with their JK Low Misalignment TRE Dust Boots (P/N 4131-11) like we did during our steering upgrade. These nitrile rubber boots stop flop in its tracks.
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