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John Retzloff: 1977 GMC K15

Truck Rear Three Quarter
Ken Brubaker
| Senior Editor, Four Wheeler
Posted November 1, 2011
Contributors: Douglas McColloch
Photographers: Sean P. Holman

Top Truck Challenge 2011 Competitors: Show & Tell

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.”


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