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A Custom-Built Cummins-Powered 1985 Jeep CJ-8 Scrambler

Posted in Project Vehicles on May 1, 2012
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We met Bruce Johnson in Silverton, Colorado, at the Mile-Hi Jeep Club’s All-4-Fun event. Johnson is an operating engineer hailing from Ashtabula, Ohio, and he has two great passions: Jeeps and diesels. Naturally, he wanted to combine the two so he built a diesel-powered Jeep Scrambler. “I have had a lifelong passion for Jeeps, especially CJs, and I wanted a reliable daily driver that got good fuel mileage. I have always been a diesel nut, too. Everything I own is diesel, including my lawn mower, so it seemed natural to combine my two passions. The CJ-8 is very rare and unique, so I thought it would make for a fun project. It also provides a longer wheelbase, so I have more cargo room and a better ride, but mostly it just looks cool,” Johnson says.

Johnson says that due to a lot of planning he didn’t run into any major setbacks during the build of this Cummins 4BT-powered ’85 Jeep CJ-8 Scrambler. “Once the engine and transmission were installed it was just assembly after that. We tried to use as many stock Jeep parts as possible, including power steering hoses, motor mounts, and clutch master cylinder. It went so well we have started many other 4BT swaps including a ’76 Ford Bronco, ’80 International Scout Traveler, ’02 Jeep TJ, and a ’06 Jeep LJ,” he says.

Johnson sourced the Cummins 3.9L 4BT turbocharged engine from a Case backhoe. Modifications are minimal and include a freer-flowing K&N air cleaner and custom 3-inch-diameter stainless steel exhaust. The powerplant is kept cool by a modified V-8-application Jeep radiator with dual Flex-a-lite electric fans. Amperage is produced by an Optima YellowTop battery that sits on a stainless steel battery tray. The engine rests on custom adapters that bolt to the factory motor mounts. Behind the engine is a salvage yard-sourced NV4500 four-speed manual transmission. Johnson says that during normal commuting the rig gets around 30 to 35 mpg.

Johnson’s rig is at home on the trail whether that trail is in Ohio or in the high country of Colorado. “I didn’t design it to be a hardcore rockcrawler, but it has handled every trail I have been on at an idle,” he notes. (It’s worth mentioning that if Johnson wants to challenge mega-gnarly technical trails he climbs behind the wheel of his aforementioned ’06 Jeep LJ, which is heavily modified and also Cummins 4BT powered.) The Scrambler is also his daily driver. “I currently drive 120 miles round-trip each day. It is a fun cruiser, but it spends most of its time hauling supplies or pulling a trailer back and forth to work,” Johnson says.

Johnson’s Scrambler is devoid of some of the bolt-ons us wheelers have become accustomed to, but don’t be fooled. Johnson has integrated his rig with a number of very cool mods that are designed to enhance the rigs function while maintaining simplicity and reliability. For example, he lives in the Rust Belt and he drives the rig year ’round, so he has made significant use of fiberglass and stainless steel components to fend off corrosion.

The Scrambler was built from the ground up using parts from a rusted-out ’85 CJ-8 that Johnson procured from the Chicago area. Parts from the ratted-out rig were integrated with a number of commercially available over-the-counter products, and his own ingenuity, to create the rig you see here. When we photographed the rig it had been assembled and driven for about seven years. It looks mellow, but its not.

The Details
Owner/Hometown: Bruce Johnson/Astabula, Ohio
Vehicle/Model: ’85 Jeep Scrambler CJ-8
Estimated value: $25,000
Type: 3.9L Cummins 4BT I-4 turbodiesel
Aspiration: Direct injection, turbocharger, K&N air cleaner, custom 3-in exhaust
Output, hp/torque (estimated): 105/265
Transmission: NV4500
Transfer case: Dana 300, 2-spd
Front: Rancho 2½-in-lift leaf springs. Monroe monotube shocks
Rear: Rancho 2½-in-lift leaf springs, Monroe monotube shocks
Front: Dana 30/open
Rear: AMC Model 20/open
Ring and pinion: 2.73:1
Wheels: 15x8 Eagle Alloy
Tires: 31x10.50-15 Goodyear Wrangler MT/R

The foundation of the CJ-8 is a mandrel-bent, 2x4-inch, 3⁄16-inch-thick Advanced Frame Works chassis (which is now available through Throttle Down Kustoms). Johnson made several modifications to the frame including sealing it and filling sections with oil to resist internal corrosion. The body consists of an extensive collection of fiberglass items from Kentrol. The list includes the body tub, hood, and fenders. The hardtop is also fiberglass. Exterior mods are minimal, but include stainless steel windshield and door hinges, hood hold-downs, and front bumper. Speaking of the doors, the half doors seen here are sourced from a Wrangler YJ, but Johnson also has full steel CJ doors with roll-up windows. The rig rolls on 31-inch Goodyear Wrangler MT/Rs that are 10½ inches wide and mounted on 8-inch-wide Eagle Alloy aluminum wheels.
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