John Retzloff: 1977 GMC K15

Truck class: If At First You Don’t Succeed
After trying for years to get into TTC, John Retzloff finally got the call-up as an 11th-hour alternate in the Truck Class. His GMC K15 certainly has the clearance for big obstacles like the Mini-Rubicon, and the bed dimensions for narrow squeezes like the Twister. It also boasts a host of owner-fabbed metalwork including the bumpers, sliders, and rear stinger.

The Details

Owner name/city: John Retzloff/Covelo, CA
Occupation: Diesel mechanic/heavy equipment operator
Vehicle model: 1977 GMC K15
Estimated value: $30,000
Engine/aspiration: Propane-injected 454ci GM Mark IV V-8, Summit racing headers, 2½-in exhaust
Transmission: SM465
Transfer case: Custom-built dual NP205s
Suspension (f/r): 52-in GM rear leaf springs, Rancho RS9000 shocks/63-in GM rear leaf springs, shackle drop, Pro Comp MX-6 shocks
Axles (f/r): Dana 60/GM 14-bolt
Axle ratio: 4.88:1
Wheels: 20-in Velocity aluminum eight-spoke
Tires: 53/16R20 Goodyear AT2A

John Retzloff, Team #44

Most looking forward to: “Probably the Tank Trap. Despite five-foot-deep water and poison oak, I love wheeling in ravines.”
Not looking forward to: “The Mini-Rubicon. If the Warthog rolled it two or three times in the middle, I know I have my work cut out for me.”
Playing on his iPod/CD player right now? “Alice in Chains’ Live, or Z-Rock 106.7 on the radio.”

The front Dana 60 is located by 52-inch rear leaf springs with an overload leaf, and dampened by six-way-adjustable Rancho RS9000s. The D60’s innards include an OX Locker, 35-spline Warn hubs and 4.88:1s. Superior axleshafts spin the 53-inch, disc-braked Goodyears, and a 49-degree long-slip driveshaft outfitted with a Longfield 300M U-joint turns the cogs. A WFO Concepts full high-steer system has been fortified by a PSC steering box, pump and ram, ORD box brace, and 1½-inch DOM tie-rods.
The front Dana 60 is located by 52-inch rear leaf springs with an overload leaf, and dampe
Inside, the K15’s cockpit has been pretty much gutted, with only the essentials remaining. Equus gauges include a tachometer, oil-pressure and temp gauges, and a dual alternator gauge. The stock carpeting was ripped out in favor of spray-on bedliner. Note also the twin shifters for the dual 205 transfer cases.
Inside, the K15’s cockpit has been pretty much gutted, with only the essentials remaining.
Big-block goodness, now propane-injected to make an estimated 350 horsepower. The 454ci Mark IV V-8’s internals have been left as they were at the factory, but it’s been aided on the exhalation side by a pair of Summit headers and a 2½-inch dual exhaust that feeds into a single Dynomax Bullet muffler with a 4-inch exit pipe. Three bed-mounted Optima RedTops (not shown) provide juice for the engine and ancillaries, and an aluminum performance radiator with dual fans helps keep the motor cool when the competition heats up.
Big-block goodness, now propane-injected to make an estimated 350 horsepower. The 454ci Ma