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4BTJ: Oil Burnin’ and 40s Turnin’ With John’s 1998 Diesel Jeep TJ

Posted in Features on September 10, 2018
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Photographers: Ken Brubaker

Four-cylinder Jeep. These aren’t typically head-turning words, but when that Jeep is painted Impact Orange and fills up at the diesel pump, you bet we’re interested. We caught up with John Reidenbach on the trail as he crawled his ’98 Jeep Wrangler TJ over some of the more challenging obstacles.

John has been through a few Jeep CJs in his wheeling days—upwards of 10. However, fond as he may have been of the leaf-sprung seven-slotters, he fell in love with the (comparatively) plush ride of the coil springs available in the TJ Wranglers. John also told us of his appreciation for diesel engines, noting the fuel economy, power, and torque of the 4BT. All it took to get his Jeep project started was a Dolly Madison bakery truck.

Among the many mods to John’s ’98 TJ are the 12-inch wheelbase stretch, 40x13.50R17LT Goodyear Wrangler MT/R tires, Warn 9.5Ti winch, and a Cummins 4BT diesel engine.

In order to create a canvas big enough for his plans, John placed the frame of his ’98 TJ Wrangler on the operating table. Using 3/16-inch steel plating, he added 8 inches to the frame’s front end. Back to the bakery truck. The bread-toting Chevy P30 Step-Van donated life to John’s project—its Cummins 4BT diesel engine. The heavy diesel-powered block needed support, which came in the form of 1-ton axles. John harvested the high-pinion Dana 60 from a seventh-gen Ford for the Jeep’s frontend, and 4 inches back from where the factory Dana 35 once sat, he placed a Currie RockJock 60. Adding to the list of brawny parts are the 40-inch tires, an Atlas 2 transfer case, and the proverbial silver bullet of transmissions—the NV4500 five-speed manual.

One of the few regrets John has about the project is weight. He envisions shaving off a few of the Jeep’s 5,500 pounds by building his custom parts from aluminum instead of steel. Despite its weight, John reports fuel mileage well north of 20 mpg. John happily wheels his Jeep on trails in Utah, Colorado, and New Mexico, noting that it rides better than his wife’s stock Wrangler of a similar model year.

Four cylinders, zero spark plugs. The Cummins 4BT, Holset HE341 turbocharger, and souped-up P-pump give John’s orange TJ the low-end torque it needs to rumble right up the red rock ledges. Behind the ’95 Dodge Ram flywheel sits the revered NV4500 five-speed manual transmission.
John chose the 3.8:1 Atlas 2 transfer case from Advance Adapters to handle the power split between the front and rear axles. Protecting the T-case and the transmission is a homemade 3/16-inch steel crossmember covered with 1/2-inch UHMW polyethylene, which lets the Jeep slide smoothly over obstacles.
The Jeep’s high-pinion Dana 60 front axle came from an ’86 Ford 1-ton. John took 2 inches from each end of the axle, added Reid Racing knuckles, regeared it to 4.56:1, and installed an ARB Air Locker. Steering is made easier with a Chevy Astro gearbox plumbed to AGR Performance’s Rock Ram hydro-assist cylinder.
Taming the Dana 60 front axle is a custom-built three-link suspension. John used 1.75-inch, 0.375-wall tubing for the uppers; 2-inch, 0.500-wall for the lowers; and Currie Johnny Joints to connect the links to the frame and axles. Fox 2.5-inch remote-reservoir coilovers with dual-rate Eibach springs handle the bounces and bumps.
John’s high-pinion Currie RockJock 60 has an air-actuated OX Locker, Ford spindles, and the disc brakes from a stock Ford 3/4-ton truck. The rear axle is held under the Jeep by a custom-built four-link suspension using the same spec tubing as the front links, Johnny Joints, Fox 2.5-inch remote-reservoir coilovers with Eibach springs, and Fox bumpstops to keep the rearend from bottoming out.
For added safety, John fabricated a rollcage from 1.75-inch, 0.120-wall tubing and bolted it to the Jeep’s frame. Cleaning the rig is as simple as pulling the drain plugs and unwinding the garden hose after John removed the carpet. The Grant Signature Series steering wheel replaced what came from the factory, while a full spread of AutoMeter gauges lets John monitor the pulse of his Jeep.
The custom fender flares and spare tire carrier were built from 1.5-inch, 0.120-diameter tubing, but only the flares were painted Impact Orange to match the Jeep. Though camouflaged well with the paintjob, a keen eye might notice the GenRight armored rear corners.
While some folks prefer hood ornaments, John’s TJ bears a custom-built brushguard, relocated turn signal lamps, Warn 9.5Ti winch with synthetic line, and an aluminum intercooler barely visible through the grille.

At a Glance


General
Vehicle: ’98 Jeep Wrangler TJ
Owner: John Reidenbach
Stomping grounds: Kenosha, Wisconsin
Build time: 6.5 months

Drivetrain
Engine: 3.9L Cummins 4BT turbodiesel
Transmission: NV4500
Transfer case(s): Advance Adapters Atlas 2
Low range ratio(s): 3.8:1
Crawl ratio(s): 97.2:1
Front axle/differential: High-pinion Dana 60 narrowed 4-in, Reid Racing knuckles, Branik Motorsports 35-spline axleshafts, stock Ford 3/4-ton disc brakes, Ford spindles, 4.56 gears/ARB Air Locker
Rear axle/differential: High-pinion full-float Currie RockJock 60, stock Ford 3/4-ton disc brakes, 4.56 gears/air-actuated OX Locker

Suspension
Front: Three-link, Currie Johnny Joints and Antirock sway bar, Fox 2.5-in remote-reservoir coilovers, Eibach springs
Rear: Triangulated four-link, Currie Johnny Joints, 2.5-in remote-reservoir coilovers, Eibach springs, Fox 4-in bumpstops

Tires/Wheels
Tires: 40x13.50R17LT Goodyear Wrangler MT/R
Wheels: 17x10 Raceline Monster 8-lug, aluminum

Miscellaneous
Steering: Jeep J20 pitman arm, Chevy Astro gearbox, AGR Performance Rock Ram steering system
Lighting: IPF Fat Boy bulbs
Armor: Custom front bumper, Bestop rear bumper, GenRight Corner Guards, custom 3/16-inch steel bellypan w/UHMW plastic skid, custom rear tire carrier, custom front and rear fender flares
Cool stuff: Frame extended 8-in (front); internal 1.75-inch, 0.120-wall rollcage; custom aluminum fuel tank; Warn 9.5Ti w/synthetic rope; Hi-Lift jack; AutoMeter gauges; Poly Performance coilover mounts; Optima RedTop battery; Sikkens Impact Orange paint; High Angle Driveline CV driveshafts; Holset HE341 turbocharger

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