Fully restored CCKW Fuel Truck gearbox
Our fuel truck's fully assembled and repainted gearbox on a stand in the shop. Note that the gear shift lever has its bakelite pommel firmly in place again. (photo via Mil-Spec Vehicle Restoration)

Our CCKW Fuel Truck is an all-wheel drive vehicle; each of its six wheels receives drive power from the engine. Indeed the K, in the truck’s designation indicates it’s all-wheel drive capability (while the first C refers to its 1941 design year, the second C means it has a standard hardtop cab and the W means it has tandem rear wheels). The CCKW’s basic chassis and drive train were employed in many diverse functions and body configurations throughout WWII and beyond (see images below). Ours, of course, served in a fuel truck configuration.

The vehicle has a relatively complex drivetrain, with power from the engine passing through the gearbox/transmission into the transfer case, which itself has drive shafts (both fore and aft) to send power to each of the vehicle’s three axles. The key component to all-wheel drive is the differential, an ingenious device made up of intermeshing gears in a housing at the center of an axle that allows the wheels at either end to rotate (under power) at different speeds when necessary. This is especially important during turns, because the wheels at the outside arc of a turn will need to rotate faster than those on the inside arc, as they are covering more ground in the same space of time. 

Mil-Spec disassembled and began overhauling the vehicle’s intermediate and rear differential units this month, carefully cleaning, then inspecting the components while replacing the bearings and seals. They reinstalled the transfer case to the chassis as well, refilling it with the appropriate lubricant and checking for leaks. The gearbox is now fully overhauled and ready for reinstallation. The team also removed each of the wheel hubs, brake drums, wheel cylinders, brake shoes and backing plates. The backing plates underwent refurbishing, although one unit was too badly damaged and needed replacing. 

The CCKW’s rear suspension depends upon a massive leaf spring assembly, one for each side of the vehicle. The images below perhaps best describe the form such a device takes. While each strip of steel (leaf) in the assembly is nested together (held in place by a set of u-bolts) each of them has the ability to slide a little with respect to its neighboring leaves. The stiffness of each leaf and the binding pressure of the u-bolts governs the springiness of the suspension. It is a simple device, but effective. This month, the restoration team refurbished the two leaf spring saddle assemblies, replacing the bearings in the pillow blocks, and then remounting them to the chassis. Stay tuned for next month’s update as more components go back onto our Fuel Truck!