Believe it or not, this is the seventh six-wheel-drive Ford that Chuck Chaplinski has built. He first concocted the fully functional tandem-axle setup 25 years ago and fitted it to an '83 F-350. With this first prototype he learned that the second rear-axle angle positioning had to be just right, the roller bearings on the output shaft of the transfer case needed to be replaced with tapered ones, and the transmission's Spicer yokes needed to be tempered steel. After fine-tuning that first truck, subsequent Fords were fitted with the same basic cab-back setup. Essentially, the back half of the '08 Super Duty's chassis you see here is more than a quarter of a century old.
A 12-volt electric over-hydraulic...
A 12-volt electric over-hydraulic ram system lifts the bed. The 8-inch air springs (2 per rear axle) go into a 3/4-inch line, which feeds into a compression chamber Chuck built out of 1/4-inch steel tubing to compress the air.
Thirty-five years building gravel-handling equipment in the concrete industry has thoroughly familiarized Chuck with one thing-how to work with steel. Couple that with an innovative mind, and you get one extraordinary truck. To make the 6x6 functional, a custom-fabricated torque-splitter divides the power that is sent to the 11 1/2-inch AAM rear axles, which have been part of the setup since 2003. The top driveshaft goes through a carrier bearing that utilizes an additional U-joint on top of the first rear axle and runs into the second axle, which is tilted slightly upward to provide the least stressful operating angle. Both rearends have Gov-Loks and 4.88 gearing.
Doing everything he could to keep the rearend cool, Chuck outfitted both rear differentials with Mag-Hytec covers, and fabricated a unique cooling system. The front axle is equipped with a remote pump that is belt-driven by the driveline and circulates gear lube fluid out of the front axle, through a cooler mounted in the middle of the truck. The cooler kicks on when temperatures reach 140 degrees F, and shuts off once the fluid has been cooled below 80 degrees.
 The rear driveshaft feeds...  The rear driveshaft feeds into a custom-fabricated torque-splitter in front of the first rear axle. A 1:1 gear ratio transfers the rotation to an upper driveshaft that runs through a carrier bearing to the second rear axle. |  The rear axle differential...  The rear axle differential is tilted upward slightly to adapt to the angle of the driveshaft. |  The 24,000-pound Super Glide...  The 24,000-pound Super Glide fifth-wheel hitch is equipped with a load cell that reads the amount of torque the truck is getting to the ground while towing a trailer. Notice the 25-gallon auxiliary fuel tank at the rear of the bed. |