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.
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.
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