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Homebuilt 1942 Ford GPW Flatfender - Science Project

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Harry Wagner | Writer
Posted November 1, 2006

Homebuilt Flatfender

When Brian Sumner first got involved in four-wheeling, he was driving a Ford Explorer. He lifted the Explorer and added some aftermarket accessories, but it soon became obvious that Sumner needed a more extreme vehicle if he wanted to explore the bevy of rocky canyons found around his home of Albuquerque, New Mexico. Sumner considered buying a built rig to save time and money, but instead he decided to build his own rig from the ground up. The rationale was that this would allow him intimate knowledge of all his Jeep's functions, and it was also a great way to put into practice the theories he was learning as a mechanical engineering student at the University of New Mexico.

A '42 Ford GPW that was rotting in his grandfather's yard served as the foundation of his project. The flatty had acted has a hunting rig for Sumner's grandfather before becoming a yard ornament for the past 20 years. Sumner and his father performed all the work on this vehicle in their driveway and two-car garage, from the tube-bending to the gear setup. The build took nearly as long as our own All-American flatfender project, but the end result is something that makes no compromises and is exactly what Sumner dreamed of.

The leaf-spring suspension is simple, yet it still provides ample articulation on the trail.

To begin, the stock GPW frame was fully boxed and fitted with outboard spring hangers to accept full-width axles. Sumner built dropped spring hangers to provide lift and allow the use of relatively flat leaf springs front and rear. A traction bar was added in the rear to keep the springs alive, and Rancho RS9000 adjustable shocks smooth out the bumps at all four corners. The suspension, in conjunction with trimmed fenders, provides enough clearance for 38-inch Super Swamper TSL tires.

Four-wheel disc brakes stop the GPW with the help of a trick Vanco Power Brake Supply Hydroboost System that fits nicely under the hood and can lock up all four 38s. The braking is needed to reign in the flatfender after bursts of speed from the built small-block. Sumner loaded the 350ci Chevy with 1.5:1 roller rockers, an Edelbrock cam and intake manifold, block hugger headers, HEI ignition, and a Quadrajet carb. From there the power is routed through an SM420 gearbox mated to a Dana 300 transfer case with a Novak adapter. This drivetrain is stout, yet it's short enough to fit in the flatfender and still allow enough room for a rear driveline.

The 'cage was fabricated from 1.75x0.120-inch HREW tubing and MIG-welded by Sumner.

Square-tube driveshafts were built with yokes from an XJ Cherokee to transfer power from the transfer case to the axles. The driveshafts are durable, offer long travel, and are inexpensive; however, they are not suitable for high speeds due to their inherent inability to balance. The rear axle is a full-floating Corporate 14-bolt with 5.13 Yukon gears, a Detroit Locker, and disc brakes that use factory Chevy rotors and calipers on custom brackets. The front axle is an eight-lug Dana 44 with matching 5.13s, a Detroit Locker, Warn chrome-moly axles, Longfield U-joints, and flat-top knuckles. Atop the knuckles sit Rockstomper steering arms that connect the axle to the Saginaw steering box and Chief hydraulic ram with 1-ton Chevy tie-rod ends and 1.25-inch and 0.219-inch-wall DOM tubing.

With the drivetrain complete, Sumner turned his attention to the GPW's sheetmetal. He knew the vehicle would be subject to hard trail use, so more effort was made to make the body safe rather than pretty. The entire floor was replaced with 14-gauge patch panels, and the rear fenders were cut all the way to the rear of the tub in order to allow the wheelbase to be stretched to 92 inches. Sumner built the 'cage from 1.75x0.120-inch and 1.25x0.120-inch HREW tube with a Pro Tools 105HD bender and a Millermatic 35 MIG welder. The 'cage is tied to the frame at six points and features a multitude of crossbars and braces. An aluminum roof was added to keep the sun and rain off of Sumner and keep rocks from entering the cab in the event of a rollover.

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