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'91 GMC

Christian Hazel
| Brand Manager, Four Wheeler
Posted May 1, 2000
Photographers: John Cappa

Hang Time--More Fun Than a Barrel of Monkeys

Step By Step

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  • The 502 engine is topped by a Holley 850 double-pumper. Underhood highlights include an MSD ignition, custom headers with 2-inch primaries, an aluminum radiator, and a tube frame.

  • The interior is dirt-simple, with Corbeau seats and a 26-point cage. A gauge cluster sits above the engine tunnel, and the hydraulic steering is actuated via a removable custom steering wheel.

  • First Engineering built the Power-Locked Dana 60 with 4.56s, as well as the four-link and sway bar. The Freightliner hydraulic steering cylinder could probably bend solid steel if given the chance.

  • A massive 14-bolt with custom bracing holds a Detroit and 4.56 gears. Braided lines ensure the brakes are properly juiced in the event of an aborted takeoff.

  • The NP205, as identified by the round plate with three bolts, is a divorced unit out of a ’76 Suburban and sits on a custom crossmember, as does the TH400 transmission.

  • The front four-link uses rod ends at all mounting points. In the event of U-joint failure, both 76-inch driveshafts are kept on-board by custom driveshaft loops.

  • The rear four-link employs massive lower arms and mild-steel tubing to locate the axle. The 502 puts out 567 lb-ft of torque, necessitating the antiwrap bars on the lower links.

  • The 38.5x16.5 Swampers on 9.75x16.5-inch Alcoas don’t rub anywhere, despite tons of axle travel. Bushwacker flares, custom Authority Motorsports bumpers, and Pro Comp 130-watt lights round out the exterior.

The expression “when pigs fly” comes to mind when watching Ramona, California, resident Billy McKim air out his ’91 GMC. Not because it isn’t a bitchin’ truck, but because he’s able to get that much daylight between the massive 1-ton axles and the ground. Billy was told by other magazines that his truck wasn’t feature-worthy. We can’t imagine why a rig that can pull duty as a hill racer, rockclimber, dune jumper, and desert blaster wouldn’t deserve some ink.

The big GMC started life as a ’91 two-wheel drive with a 4.3L V-6, but when you get down to it, there isn’t much left other than the body and part of the frame. A GM Performance Parts 502 crate engine was set back 13 inches into the cab for better weight transfer. Backing the Rat is a built TH400 on a custom crossmember and a divorce-mounted NP205. Equal-length driveshafts connect to a Dana 60 front and a Corporate 14-bolt rear axle that were massaged and trussed by First Engineering in Ramona.

Billy had First Engineering create a custom tube front frame, and Authority Motorsports create a custom tube rear frame in anticipation of the four-link front and rear suspension. The Eibach springs on King coilover shocks are equally comfortable soaking up big-air landings as they are at high-speed desert running. In order to control the big 38.5-inch Swampers in deep sand and at slow speeds, a hydraulic steering valve from a Freightliner was fitted and powered by a Rupes Hydraulics pump. The hydraulic steering is so powerful that Billy can place a tire against an obstacle and move the truck sideways by turning the wheel.

On the inside, a 26-point rollcage (that’s not a misprint) surrounds the Corbeau buckets and Auto Meter gauges, and, as Billy found out in a recent rollover, it really protects the occupants from serious injury. A 2000 GMC body is being prepared to replace the old crunched sheetmetal, but in the meantime Billy will continue to rack up the frequent flier miles.