Fab Fours and MarsFab Build a Custom Lifted Wrangler JL

Jeep had been teasing the new Wrangler JL for months before we were finally able to see one for ourselves on the showroom floor. When the all-new JL was finally available and most people were happy simply to take one for a test drive, Fab Fours—the company known for creating incredibly innovative bumper systems for a variety of vehicles—had already put down cold, hard cash for not one, but two brand-new JLs.

One of the new Wrangler Unlimiteds was used for internal R&D for new bumper systems, while the second was driven to MarsFab OffRoad in Harrisburg, NC, for some pretty serious suspension upgrades. Fab Fours is known for building some eye-catching showpieces (for examples, check out our coverage of the Kymera or The Legend), and now the company wanted a show-stopping JL to take to (and abuse at) the Easter Jeep Safari. So, before the 2018 Wrangler even had a thousand miles on it, MarsFab was ripping it apart to create a big-time rockcrawler with a custom-fabricated suspension system.

While most of us had yet to see one of the new Wrangler JLs in person, MarsFab Offroad was already ripping into an Unlimited model for a custom build.

Since there weren’t any aftermarket lift kits for the JL yet, the plan was to fabricate a custom suspension system from scratch capable of handling a set of 43-inch tires with ease. Meanwhile, the crew at Fab Fours used the second JL as an R&D mule to develop an updated Grumper, Vicowl and fenders that all work with the new Jeep.

Upgrading The JL

Jeep Wranglers are likely the most modified vehicle in the history of transportation, but the JL’s complexity makes things difficult. “The new JL is a nice Jeep,” said Chris Marshall, owner of MarsFab. “It’s definitely one of the nicest Wranglers yet. But there’s a lot of technology and complexity packed into it now, and that makes it a bigger challenge when trying to modify it to your tastes.”

On the left is the stock rear suspension; for comparison, the right shows the suspension after MarsFab had finished fabrication. The team ratcheted the housing all the way up to check for clearance at full compression.

There’s no doubt that the new JL should still be a capable off-roader, but many of the changes were made to help improve fuel economy. For example, the new JL comes with a center axle disconnect to help reduce rolling resistance. The problem with the decoupler is that it uses a sliding sleeve to lock the front axle to the diff, which introduces a potential failure point when doing serious off-roading. What’s more, the shift mechanism is electronically controlled. Removing it causes the onboard computer to throw a trouble code, potentially sending the engine into limp mode.

Marshall had no intention of keeping the stock axles, and had planned with Fab Fours to install upgraded ones at both ends. In fact, Fab Fours reused 5.38:1 axles from a previous MarsFab build; MarsFab had already gone through and installed new 5.38:1 gears and Detroit Lockers. Up front is a Currie Enterprises high-pinion 9-inch, while the rear is a Currie low-pinion 9 inch. The front was outfitted with a set of Dodge Ram dual piston calipers. The rear, meanwhile, retains the factory JL rotors and calipers; they will work with the Currie housings and chromoly axles.

Marshall and Zuber discovered that simply deleting the electronically controlled center axle disconnect shifter wasn’t possible because leaving it unplugged would throw a trouble code to the ECU. And there aren’t yet programmers on the market for the brand-new JL. So they came up with an ingenious solution. MarsFab pulled the stock front axle and the shifter fork off the selector unit, then built a bracket to hide the selector unit safely out of the way under the hood. The selector unit is still plugged in—even though it doesn’t do anything—so the computer is happy and there’s no temptation for the ECU to throw the Jeep into the dreaded limp mode. Marshall stresses that this is just a band-aid, and as soon as programmers become available he’ll bring the JL back into the shop and delete the axle disconnect system completely.

Connecting the axles to the frame is a completely custom suspension MarsFab fabricated to get tons of articulation with the 43-inch tall tires without cutting any more of the body than necessary. By carefully locating the link locations and moving the front axle forward two inches, Marshall and Zuber were able to get the big tires to fit and move throughout the 12 inches of shock travel with only three inches of lift. That helps keep the center of gravity lower so that the Jeep doesn’t get too tipsy on the rocks.

Underneath the upper link mount you can see the box that switches the decoupler on the front axle. There isn’t a programmer on the market yet for the JL to allow deleting this system, so MarsFab kept the box–even though the entire front axle has been swapped out–and simply tucked it out of the way in a custom mount. Now the ECU sees that it is still attached so it won’t throw the engine into limp mode.

The new links are all made from steel tubing in a variety of diameters and wall thicknesses. For maximum strength, the lower links are made of 2.25-inch diameter tubing with a 3/8-inch wall. The single upper link on the front is 1.75 diameter with a  3/16 wall, while the two uppers in the rear are 1.50 inches in diameter and with a 1/4-inch wall. The heims are weld-in chromoly Enduro Joints from Barnes 4WD.

Getting those big, beefy links, front and rear track bars, and the steering linkages to all fit together was a bit of a puzzle, especially while trying to maximize wheel travel. As you can see from the photos, things got pretty tight at full compression, but careful placement of all the suspension points allowed it all to work.

Damping is provided by a set of four King air shocks that MarsFab sourced through Poly Performance. These shocks are 2.5-inches in diameter with 12 inches of travel at all four corners. Nitrogen charging the shocks replaces the need for springs to simplify the suspension setup, and right height can be adjusted by adding or bleeding off some nitrogen. The bump stops, by the way, are also from King with two inches of travel. The King bump stops are pretty trick; they even come with the steel sleeves that MarsFab used to mount the bump stops to the frame.

All the heim joints are Enduro Joints from Barnes 4WD, just like MarsFab owner Chris Marsh uses on all his scratch-built buggies. The linkages are laser-cut in-house from 1/4- and 3/16-inch plate and welded in double-shear whenever possible for strength (in some photos, the mounts are only tacked in place before final welding). Finally, you can see the mount Marsh had to come up with to keep the track bar in proper alignment without hitting the steering linkage. Things definitely got tight with all the moving parts, but Marsh found a way to make it all work.

MarsFab normally builds hardcore buggies and rock bouncers from scratch, so fabricating a custom suspension from a pile of tubing is the norm for them. Still, the JL threw out a few hurdles. “After tearing into it, I really do like the new Jeep, but there are two sides to it,” Marshall said. “It’s definitely more solidly built than previous Jeeps, and it has a lot of modern conveniences that people are used to seeing in cars and trucks. The downside of that is there are electronic systems controlling everything.”

Marshall was specifically referencing the steering system. For the new JL, Jeep’s engineers switched from a traditional, belt-driven power steering pump to an electric pump. The idea is to reduce demand on the engine to save a little gas for the mall-crawling crowd. In addition, the steering unit also uses a lightweight cast aluminum case. This all might be fine, but it understandably caused a little worry for the folks at both Fab Fours and MarsFab, who worried about the stress the larger tires and a little rock crawling would put on these components.

To fix that, MarsFab turned to PSC Motorsports for their heavy duty Big Bore XD steering box. This box is designed for the previous-generation JK Wrangler, but the only real difference is the bolt locations for mounting the box to the framerails. MarsFab fixed this with a new laser-cut bracket. To help move the beefy rubber, MarsFab also added a PSC 2-inch diameter, 6.5-inch travel steering cylinder, actuated by hydraulic hoses tapped into the steering box. There was no traditional power steering pump replacement for the JL yet, so the electric pump was retained.

Marshall says he did hear rumors that if the power steering fluid or pump got too hot, the sensors would pick it up and kick the Jeep into Limp Home Mode. To keep that from happening, a Derale power steering cooler with its own integral electric fan was plumbed up and installed on a custom bracket that placed it in front of the radiator.

On the left, you can see the front suspension in full droop. Notice that this is a three-link, with an upper link only on the passenger side. This was done for room; both the steering and the stock exhaust on the driver's side made this the best solution. In the center, fabrication specialist Andy Zuber checks for interference issues when the steering is racked fully to the left and right at full compression. On the right, you can see the custom bracketry MarsFab fabricated to secure the King air shocks, as well as the bump stops. It should stand up to plenty of abuse.

Interestingly, the Jeep’s steering never overheated, but it appears the electric power steering pump may have had a little trouble keeping up with increased demand for power. “The steering was a bit limited trying to turn left,” explains Fab Fours’ Kermit Baker. “This may have caused us the most trouble on the trails. It was more of a nuisance than a crippling issue, but hopefully, we can figure out a way to make that better, too.” Likely, Kermit adds, the solution will be a new power steering pump from PSC as soon as they finish science-ing out the details.

When Fab Fours debuted the JL at the Easter Jeep Safari, Baker says the MarsFab suspension performed very well. “We took several vehicles out there, and the MarsFab Jeep turned out to be our go-to vehicle,” he says. “It worked almost flawlessly the entire time in Moab. We hit quite a few trails throughout the week and thought we did a good job testing the limits of the new JL on some of the harder obstacles in Moab.

“I was pleased with the approach angle and clearance that our new second-generation Grumper and Fender system provided,” continued Baker. “All around, MarsFab did a terrific job with the JL’s setup. We were able to drive it 55-60 miles per hour down the highway with ease, and then drive it through whatever Moab had in store for us on the trail.”

There was no sense keeping the wimpy stock spare wheel and tire, so MarsFab came up with this trick license plate holder/spare tire delete. Besides being super-sanitary, it also allows the Wrangler's rearview camera to be reinstalled securely inside the housing, and it even maintains the correct angle. MarsFab will be producing the license plate holder for other JL owners as well.

“One small issue we did notice with the Jeep is it didn’t seem to like steep inclines,” commented Baker. “A couple of times, we noticed a considerable amount of white smoke pouring out of the exhaust after hill climbs. We aren’t sure of the cause as of yet. Maybe it’s oil going through the PCV valve? We aren’t sure yet, and wondering if other off-roaders will have the same issue with their new JL Wranglers.”

FabFours is famous for their aggressive-looking Grumper and Vicowl systems for Jeeps, and the company created a new evolution of both for the new JL. Incredibly, MarsFab only had to trim small bits to get the Grumper to work with the giant 43-inch meats, even with all the suspension's incredible articulation. So the FabFours Grumper and fender flares should work with practically any reasonable lift kit and tire combination. We like that the new Grumper for the JL incorporates the Grumper right into the fender flares for an even more aggressive look.

In the future, we’re sure plenty of aftermarket companies will come forward with lift kits and other upgrades for the new Wrangler JL. But the bar has already been set pretty high thanks to Fab Fours’ and MarsFab’s collaboration on this Wrangler Unlimited right out of the gate!

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About the author

Jeff Huneycutt

Jeff Huneycutt has been in the automotive industry long enough to collect more project cars than he can afford to keep running. When not chasing electrical gremlins in his '78 Camaro, he can usually be found planning unrealistic engine builds.
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