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Rollin' in a Cummins-powered Jeep J20

Posted in Features on October 1, 2015
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Photographers: Brotography PA

Mitchell Zimmerman decided at a certain point in his life that he was going to drive nothing but Jeeps. He already had a Wrangler so that was a no-brainer, but he also wanted a pickup truck. The Pennsylvania resident found what he wanted in Illinois, so he drove over and bought a near-perfect condition Comanche. It had the low-output 4.0L engine and leaked a little oil. (An old Jeep leaking oil? Naahhh.)

He came up with the plan to do a Cummins 4BT or Mercedes diesel swap into the Comanche, and because he heard the guys at Zion Offroad in York, Pennsylvania, had done quite a few successful diesel conversions, he headed over in his Comanche for a quote. Low and behold, what should Zimmerman spy when he got to Zion Offroad? It was a '88 Jeep J20 pickup truck that appeared to be in pretty good shape. Well, that sight started a conversation, and before he could say '88 Jeep J20, it was his in trade for the Comanche. Since then, Zion Offroad has replaced the engine in the Comanche with a high-output 4.0L, but that's not really what this story is about.

Chassis
Before Zimmerman set eyes on the J20, it had already received some work from Zion Offroad. The frame had some considerable rot when they got it, but other than that, the truck was in decent condition. The guys realized that the J20 frame was within a 1/2 inch overall length of the frame sitting under a '92 Dodge 2500 Cummins pickup they had in the shop. It didn't take long for them to have that frame under the J20 body, and that allowed the mounting of a 3.54 Dana 60 up front and a 3.54 Dana 70 in the rear. The stock suspension was kept and 37-inch Pro Comp tires and 17-inch Pro Comp wheels were mounted up. Wonder how it works? Zimmerman said the truck scored a 560 on MetalCloak's CTI ramp—not bad for a 1-ton pickup truck.

Engine
The Cummins powertrain was moved back 4 inches on the Dodge frame to fit within the J20 cowl and make room for the custom radiator with no firewall mods needed. Then Zimmerman went to work to really "make it his." The 5.9L had a water pump leak, but he decided to not stop at simply replacing that. He had East Coast Diesel of Jonestown, Pennsylvania, help him rebuild the engine using a BD Power Fuel Pin, Dynomite Diesel 150HP Stage 3 55LPM injector set, and a BD Power Super B Turbocharger. To help the engine run cooler, he installed a Snow Performance Stage III Water Methanol Injection System and placed the water/meth pump and a 7-gallon tank in a bed-mounted toolbox. A K&N intake filter system and a custom straight pipe exhaust were also added. He made a custom CNC valve cover for the 5.9L, and a South Bend clutch channels power to the Getrag five-speed manual transmission. Zimmerman also sandblasted and repainted many of the engine components to make it all look like new.

Cabin
For the interior makeover, Zimmerman worked with James Long Upholstery Studio in Mount Joy, Pennsylvania. The J20 received new black carpet, the dash was dyed black, and a set of Wagoneer power seats were reupholstered in black vinyl with silver cloth inserts. Posies Rod And Custom of Hummelstown, Pennsylvania, installed a Vintage Air electronic air conditioning and heating system and did a complete instrument swap using Dakota Digital display panels and instruments for everything except for the EGT and boost, which are Auto Meter gauges. A Bluetooth-capable radio makes hands-free phone calls possible, and Dakota Digital electronic door locks and remote entry system mean no fumbling with keys on dark cold nights. For added comfort and quiet, the entire cabin was lined with Dynamat and Dynaliner.

Body
Exterior adornments were kept simple but functional. Zion Offroad made some custom bumpers for the J20, and a late-model Wagoneer grille fronts the truck. Zimmerman added a set of Rigid Industries LED lamps in custom mounts on the rear bumper to act as reverse lights, and a pair of Truck-Lite LED headlamps brings the Jeep's forward-facing lighting into the 21st century. He also built a custom mount for the front bumper that enabled the use of a Quadratec 10,000-pound capacity Competition Series winch. The winch is set up with synthetic cable, and a Factory 55 flatlink attachment dead-ends the cable. The J20 is coated in Jeep Deep Water Blue Pearl paint. The body and paint work were done by Engles Frame and Body and Dale Lee Auto Body, both in Ephrata, Pennsylvania.

Zimmerman told us, "When I sit in some of my friends' shiny new vehicles, I do admire the supple seating and the fantastically modern infotainment center, and occasionally I even crave the fuel economy and neck-jerking acceleration. However, I just can't imagine owning such a mundane contraption—It feels like piloting an Android or iOS device." We can't argue with that. Zimmerman continued, "When I turn the key in my J20, I am instantly rewarded with the glorious growl of a Cummins under the hood and the satisfaction that I'm driving an off-road machine that rattles, squeaks, hums, and delivers a visceral experience that makes me smile all day long."

HARD FACTS
Vehicle: '88 Jeep J20/1992 Dodge 2500 frame
Engine: '92 5.9L I-6 Cummins diesel
Transmission: Getrag five-speed manual
Transfer Case: NP 205
Suspension: Stock leaf springs and shocks
Axles: Dana 60 front, Dana 70 rear, both 3.54 gears
Wheels: 17-inch Pro Comp
Tires: 37-inch Pro Comp
Built For: The joy of driving something unique

Why I Wrote This Feature
It's a 5.9L Cummins in a Jeep J20 pickup on a Dodge 2500 frame. Any other questions?

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