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1981 Jeep CJ8 Winner - 2005 Top Truck Challenge Winner

Posted in Top Truck Challenge: 2005 on December 1, 2005
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Photographers: The Four Wheeler Staff

So what is it about Jerry Duffy's Jeep CJ-8 that makes it capable of winning Top Truck Challenge? Was it built with a no-ceiling budget? Is it a highly advanced computer-generated and tested design? Does it have the latest traction-control electronics? Actually, no. None of the above. Duffy's rig is simply a collection of components and modifications that work very well together. Of course, those things didn't just magically jump onto his rig.

He purchased the Scrambler in 1999 in his home state of Idaho with the plan of eventually building it up. Well, that "eventually" ended up being right away because the transmission took a dump on the way home. "I was really ticked," he remembers. It wasn't long before the Jeep was scattered all over his garage. His goal was to build the Jeep around himself and his driving style. He also wanted it to be proficient on all types of terrain. Since Duffy was retired, he was subject to a fixed income, so it had to be done right the first time. Interestingly, he began the buildup with the engine and went from there.

What follows is a detailed overview of what makes his CJ tick. Clearly, there's another part to this equation, and that's driver experience. When Duffy's 47 years of 'wheeling experience is combined with the CJ's proven components, it becomes clear why he's our Top Truck Challenge winner for 2005.

The frame and body of the CJ have undergone some significant changes. The frame was chopped right behind the front seats, and a new tapered frame made from 1.75-inch-diameter chromoly tubing was put in its place. This created a longer 112-inch wheelbase, a better departure angle, and decreased the width of the tail end of the rig. A custom 20-gallon aluminum fuel tank is mounted high in the new frame above the fuel pump. The 1.75-inch-diameter rollcage and frame are one unit. On the outside, the grille assembly was moved 2 inches forward to make room for the radiator and fans (remember, this rig was designed around the engine). The hood was lengthened to compensate and louvered to assist in cooling. The front fenders are made from 1-inch-diameter tubing and 16-gauge steel; the windshield and cowl are stock; the half-doors are off a YJ; and the custom rear fenders are made from 16-gauge steel. Significant modifications have also been made to the rocker panels. "It took me over two weeks labor on each side to cut 4 inches up and 4 inches in and create a new 45-degree angle rocker," Duffy says. The result is a rocker that is less prone to damage and hanging up on obstacles. Further, Duffy didn't like the way the body mounts hung down and caught on obstacles, so he moved them 1-inch upward on the frame. Finally, there are no bumpers on the rig, and the four clevises are bolted directly to the ends of the frame, as is the front-mounted Warn 9.5 XP winch.

"I felt like I'd need rear steer after extending the wheelbase, but its turning radius turned out to be very good," Duffy says. Nonetheless, it's under there now and it's good for those tight situations. A rocker switch conveniently located right next to the transmission shifter allows Duffy to activate the hydraulic rear steer at will, and this system features a number of beefy upgrades just like the front steering. The rear axle is a Dynatrac 60 which, like the front axle, features an ARB Air Locker, 5.13:1 Yukon gears, Superior 35-spline, 1.5-inch-diameter axleshafts, and disc brakes. The flexy rear suspension is a triangulated four-link with Alcan elliptical springs, King Racing 14-inch-travel remote-reservoir shocks, and limiting straps. Spherical rod ends are used all around.

Torque. It's what this ZZ 502 big-block engine is all about. "I ordered this TPI crate engine from the folks at Street Performance in Arkansas, and then I had them grind a cam especially for my needs," Duffy says. They looked at him funny when he told them what he wanted, but he's ecstatic with the results. "It makes over 600 lb-ft of torque right off idle, and approximately 650 lb-ft of torque max," he proudly notes. Duffy didn't sacrifice horsepower, though, as the engine produces more than 400 ponies. Due to a number of upgrades to lighter aluminum components, the engine weighs only 90 pounds more than a Chevy small-block. The result is a lightweight, trail-friendly big-block engine that can lug all day long. It's cooled by an aluminum Ron Davis radiator that has switchable dual electric fans. It exhales through ceramic-coated block hugger headers and a single 3-inch-diameter exhaust with glasspack muffler. Other underhood mods include a York engine-driven compressor, a 230-amp alternator (with homemade milk jug cover to keep water out), and an Optima Yellow Top battery. All of this power is routed through a 4L80-E automatic transmission with shift kit and TCI stand-alone computer. The transmission is kept cool by a rollcage-mounted Flex-A-Lite cooler with fan.

Splitting the power to the axles is an Atlas II 3.8:1 transfer case with 35-spline yokes. Torque is carried to the front axle via a custom Six States driveshaft with 1350 U-joints and a High Angle Driveline rear driveshaft with 1350 U-joints at the transfer case and 1410 U-joints at the axle.

Up front, there's a tried-and-true Dana 60 out of a 1979 Ford F-250, and it has more than enough beef to handle the big 44-inch-diameter Super Swamper TSL tires on Champion bead-lock aluminum wheels. The axle features an ARB Air Locker, Yukon 5.13:1 gears, and 35-spline, 1.5-inch-diameter Superior axleshafts. Duffy made darn sure the steering was up to the task of hard trail use by installing hydraulic assist comprised of a Howell pump and reservoir and an AGR Rock Ram. Other beefy steering components include a Dodge 3/4-ton pitman arm, a 1.25-inch-diameter drag link, custom high-steer arms made from 3/4-inch plate steel, and a 1.25-inch-diameter tie rod. The front suspension is a custom johnny-jointed three-link with 14-inch-travel King Racing remote-reservoir coilover shocks (with Eibach springs), and a Currie antiroll bar. Limiting straps keep the suspension from over-extending, and the straps are adjustable.

You'd expect a trail rig like this to have a thrashed interior, but that's not the case. The entire tub is Rhino Lined, and there are Mastercraft front and back seats. The steering wheel is by Grant, and it's bolted to a tilt column. A full array of Auto Meter gauges reside in the custom dash, and they allow Duffy to monitor his speed, engine rpm, oil pressure, coolant temperature, voltage and transmission temperature. Securely mounted in the rear of the Jeep are a jack, extra fuel and various tools.



Jerry Duffy, Twin Falls, Idaho
1981 Jeep CJ-8
Estimated Value:
Top Truck finishes

Trail Fix
Frame Twister
Mud Pit
Hill Climb
Obstacle Course
Tow Test
Mini Rubicon
Tank Trap

502ci {{{Chevrolet}}} ZZ V-8
TPI fuel injection, ceramic-coated block hugger headers, custom 3-in.-diameter exhaust, glasspack muffler
Output, hp/
torque (lb-ft):


4L80-E automatic, TCI computer, Flex-A-Lite cooler, Art Carr shifter
Transfer Case(s):
Atlas 3.8:1 with 35-spline yokes

Triangulated three-link, 14-inch-travel King Racing remote-reservoir coilover shocks with Eibach springs, adjustable limiting straps
Triangulated four-link, Alcan elliptical springs, 14-inch-travel King Racing remote-reservoir shocks, limiting straps

Dana 60, Superior 35-spline 1.5-inch-diameter axleshafts, Howell steering box, pump, and reservoir, AGR Rock Ram, Dodge pitman arm, custom high-steer arms, drag link, and tie rod/ARB Air Locker
Dynatrac 60, disc brakes, Superior 35-spline 1.5-inch-diameter axleshafts, hydraulic steering/ARB Air Locker
Ring and pinion:
Yukon Gear 5.13:1

15x10 Champion bead locks
44x15.50-15 Super Swamper TSL

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