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  • JP Magazine
  • Dirt Sports + Off-Road
  • 4-Wheel & Off-Road
  • Four Wheeler

1989 GMC Jimmy - Decked Out

Posted in Features on May 1, 2013
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As is often typical in off-roading, each wheeling trip that Glenn Decker took in his 1989 GMC Jimmy was the catalyst for upgrades. A couple of axles here, a new transmission there, and pretty soon there were upgrades everywhere. But Decker, a stay-at-home dad/stereo system fabricator from Rancho Cucamonga, California, kept buildup costs down by sourcing many used parts. For example, he found a used Offroad Design Doubler for sale on an Internet site and a set of used 42-inch Swampers on double beadlock wheels for sale in Arizona.

The exterior of the Jimmy is like a how-to lesson in making a fullsize truck more trail capable. With the doors and hardtop removed, Decker has vastly improved visibility. He created more body-to-ground clearance and more room for the 42-inch Super Swamper TSLs (on Humvee double-beadlock wheels) by installing a 2" Energy Suspension body lift. Protecting the rocker panels is a pair of custom 2x3-inch, 0.250-inch-wall rock sliders. Decker can illuminate even the darkest trails thanks to three bumper-mounted ACRO HID flood lights, six roof-mounted HID lights, and eight Vision X LED lights mounted underneath the truck. Up front, the stock fenders have been replaced with a pair of race-style fiberglass fenders and the hood is completely removable and affixed by four hood pins. By now you’ve probably noticed that front of the rig doesn’t look like an ’89 GMC Jimmy. That’s because it has been updated with Chevy truck parts, circa 1992. The truck is painted Krylon Sunrise Red (yep, it’s a rattle-can paint job, 12 cans to be exact).

Also as is typical, the '89 Jimmy is an ongoing project. Decker says he plans to add an ARB Air Locker to the front differential, PSC hydro-assist steering, and possibly a four-link front suspension.

A couple of axles here, a new transmission there, and pretty soon there were upgrades everywhere.

We found Decker prowling around the southern California desert and we were impressed at his work thus far and his dedication to wheeling a fullsize rig. Decker has done a great job of decking out his rig.

PhotosView Slideshow

At A Glance
Vehicle: 1989 GMC Jimmy
Owner: Glenn Decker
Stomping grounds: Rancho Cucamonga, California
Build time: 6 years

Engine: GM Performance 350ci V-8, TPI, Doug Thorley headers, Magnaflow muffler
Transmission: Modified TH400
Transfer case(s): NP203/205 Offroad Design Doubler
Low range ratio(s): 2:1, 4:1
Crawl ratio(s): 22.6:1, 45.2:1
Front axle/differential: Dana 60, Yukon 35-spline chromoly axleshafts, Warn manual hubs, ORD high-steer and crossover steering/4.56 gears, open
Rear axle/differential: GM 14-bolt, Yukon chromoly axleshafts/4.56 gears, Detroit Locker

Front: Deaver Suspension leaf springs, Rancho RS9000 shocks, polyurethane bumpstops
Rear: Deaver Suspension 57-in leaf springs, Rancho RS9000 shocks, polyurethane bumpstops
Steering: Chevy 2WD steering box, ORD pitman arm, ORD crossover and high-steer system

Tires: 42x15.00-16.5 Interco Super Swamper TSL
Wheels: 16.5x9.75 Humvee double beadlock

Armor: Custom front bumper, custom rock sliders, custom rear bumper, custom rollcage
Cool stuff: '94 Chevy Grille, custom cargo area storage, lots of exterior lighting, rock lighting, front-mounted Mile Marker SE 12000C winch

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