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1998 Jeep Wrangler TJ - Grunt

Posted in Project Vehicles on June 1, 2010
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We find most of our features on the trail, but every once in a while we run across a Jeep in an odd location that catches our eye for some reason. Sure, the parking lot of the Spanish Trail Arena where the vendors set up for the show at the end of Moab Easter Jeep Safari might not sound that weird, but when you figure that there are hundreds of Jeeps in the parking lot that we hardly even look at, this TJ stood out.

With a low stance, big tires, and fresh Impact Orange paint, it is little wonder it stood out. So Trasborg pulled his normal crawl-around-and-under-the-Jeep routine, hoping he wouldn't get shot if the owner came out and found him. It didn't take too long to see the custom fuel tank and Dana 60s, but when he saw that there was a Cummins 4BT under the hood rather than a Chevy small-block, he was hooked.

A business card left in the windshield resulted in a call from the owner, John Reidenbach. About 15 minutes later, we found out about the combination of Dodge Ram, Ford, and owner-built parts that make it possible, so we quickly set up a time to go wheeling and check out this Jeep some more.

The stock TJ frame was cut in the front and stretched to accommodate moving the front axle eight inches forward, but the rear was merely cleared of all the stock suspension brackets. Both front and rear were plated where the holes and mounts for the stock upper control arms used to be to provide stronger mounts for the new links. An owner-built engine cage/radiator mount/shock mount locates some 14-inch Fox coilovers up front, while the same coilovers hang from some Gen-Right coilover buckets out back.

Up front, a three-link with panhard rod locates the front axle with a Currie Antirock bar for sway control, and a double-triangulated four-link pushes the rear axle back about four inches with all the links using Johnny Joints at every end. The flat belly skid is home-built, protects the rear link mounts, and is lined with UHMW polyethylene to more easily slide off rocks. The aluminum fuel tank and matching steel skidplate are also owner-built and designed to clear the rear axle and maximize fuel capacity at the same time.

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It all starts with the swapped-in Cummins 4BT four-cylinder diesel. Instead of the huge water-filled mounts that held the engine in the donor vehicle, John moved the stock 4.0L motor mounts to locate the Cummins. He then bolted it to an NV4500 out of a diesel Dodge Ram using the flywheel, clutch, starter, and adapter out of the Dodge to bolt it together. A 3.8:1 Atlas II handles reduction chores and sends power on to the axles through High-Angle Driveline driveshafts.

The front Dana 60 was nabbed out of a Ford and narrowed 41/4 inches and stuffed with an ARB Air Locker. Out back, a Currie Iron Jock centersection was tubed locally and the ends of the tubes have flanges to accept Ford Dana 60 spindles, hubs and brakes. The Ox Locker in the rear is pneumatically activated by the ARB compressor and both axles received 4.56 gears to keep the diesel engine rpms down low while turning the 40-inch Goodyears. With no provision to run a vacuum booster, a hydroboost setup off a '91 Chevy P30 van was used to provide plenty of line pressure.

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Body and Interior
The stock TJ tub was modified to allow enough uptravel for the rear links. Then it was pulled off the frame and painted Impact Orange. Homemade rear flares adorn the Gen-Right Crusher corners while a Smittybilt rear bumper and ORO Light Dots finish off the rear. Up front, the high-line tube fenders were built by John with the hood cut to match and the grille tilted forward from the stock location. The front bumper is a Blue Torch Fab piece but the grille hoop is a homemade unit.

The cage inside the Jeep is also homemade and works with the stock seats to provide a solid base for them. The transmission tunnel had to be clearanced for the big NV4500. A bevy of Auto Meter gauges is located in the center stack of the dashboard, including a pyrometer, a boost gauge, fuel, water, and oil gauges. The stock TJ speedometer and voltmeter still work and John is investigating how to hook up the stock TJ tachometer rather than swap the stock cluster out. By keeping the TJ cluster, John has kept many of the stock indicator lights as well.

A Grant steering wheel takes the place of the stock one, and with the cancelling arm off of the clockspring grafted onto it, the turn signals not only work, but cancel just like they would with the stock steering wheel. A button on the steering column now activates the horn. Thanks to the transmission tunnel and floor modifications, no carpet kit will fit this Jeep unless it is custom-made, so John had it sprayed with U-POL bedliner that was tinted to match the paint. Sprayed inside and under the tub, it does a good job of cutting down on noise.

Good, Bad, and What It's For
It's low, it's orange, and it works great. We saw this Jeep before it was finished, so we can't knock things like gauges not working or the cage not being plated or tied into the frame. We thought that the engine would rip the TJ six-cylinder engine mounts in no time and that the TJ mounts would transmit a lot of vibration to the chassis, but John says that with 5,000 more miles on it since we saw it, the mounts are still fine. We'd have tossed the TJ cluster to begin with and built a custom one to fit the space.

Hard Facts
Vehicle: '98 Wrangler
Engine: '91 3.9L Cummins 4BT
Transmission: '95 Dodge NV4500
Transfer Case: 3.8:1 Atlas II
Suspension: Four-link (front), four-link (rear)
Axles: '89 Ford Dana 60 (front), Currie Rock Jock (rear)
Wheels: Allied Racing Rock Monster
Tires: 40x13.50R17 Goodyear MT/R
Built For: Real Jeeps run diesel fuel.
Why I Wrote This Feature

Cappa says, "The 4BT sounds like a bunch of marbles shaken in a can and vibrates too much to drive comfortably." Hazel says, "Who would want to breathe diesel fumes all day long on the trail?" I didn't agree with them; I love the smell and sound of a diesel-powered rig. I think a Jeep engine should have plenty of power down under 2,000 rpm, and what better way to get there than with a diesel? I have wanted to build a 4BT-powered Jeep for quite a while, much to Cappa's and Hazel's disagreement. After seeing this one on the trail and getting to drive it, I've got the bug even worse. It doesn't knock out your fillings, it's got gobs of power where it should, and the low-slung, long-arm setup works great off-road and rides great on-road.
-Pete Trasborg

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