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GMC CCKW 2½-ton 6×6 truck

The GMC CCKW, also known as "Jimmy", or the G-508 by its Ordnance Supply Catalog number, was a highly successful series of off-road capable, 21⁄2-ton, 6×6 trucks, built in large numbers to a standardized design for the U.S. Army, that saw heavy service, predominantly as cargo trucks, in both World War II and the Korean War. The original "Deuce and a Half", it formed the backbone of the Red Ball Express that kept Allied armies supplied as they pushed eastward after the Normandy invasion.

Etymology
The name CCKW comes from GMC model nomenclature: • "C", designed in 1941 • "C", conventional cab • "K", all-wheel drive • "W", dual rear axles • "X", experimental chassis / non-standard wheelbase (first 13,188 units ) ==History==
History
In 1939 and 1940, the US Army Ordnance Corps was developing load-rated (off-road rating) 6×6 tactical trucks that could operate off-road in all weather. General Motors, already supplying modified commercial trucks to the Army, modified the 1939 ACKWXbuilt for the French Armyinto the CCKW. The General Motors design was chosen by the Army and went into production at GM's Yellow Truck and Coach division's Pontiac, Michigan plant alongside 6×4 CCWs. Later, they were also manufactured at GM's St. Louis, Missouri Chevrolet plant. ==Production numbers==
Production numbers
Sources do not precisely agree on the total numbers of CCKWs built by the end of production in 1945. Ware (2010) lists one single number of 562,750 of CCKW trucks, built across all variants—presumably including the amphibian DUKW. More clearly specified numbers are provided by Sunderlin in Army Motors magazine, and by Jackson, using the numbers found in the 1946 revision of the U.S. military's Summary Report of Acceptances, Tank-Automotive Materiel. Sunderlin reports a total of 528,829 of -ton 6×6 units (excluding the DUKW) produced by GMC—versus a total of 527,168 accepted by the U.S. Army. Jackson's tabulation of the 1946 U.S. acceptance numbers adds up to 524,873 units, excluding the DUKWs and the ACKWX predecessor models. Both of these numbers still include the cab-over engine AFKWX-353 models—leaving a total of some 518,000–519,000 actual CCKW-352 and CCKW-353 units. In addition, GMC serial numbers indicate a production of 23,500 of the same bodied 6x4 CCW models, versus 23,649 units accepted by U.S. ordnance. In any case, GM / GMC built a total number of -ton, 6-wheeled trucks that was second only to the WWII "Jeep" —and neither Ford nor Willys individually built as many jeeps during the war. ==Specifications==
Specifications
Engine and drive-line The CCKW was equipped with the GMC 270 engine, an overhead valve inline-6 with or at 2,750 rpm, and at 1,400 rpm. A bore by stroke gave a displacement. This gasoline engine was designed for commercial trucks, and was reliable in service. The transmission was a Warner T93 5-speed with a direct 4th gear and overdrive 5th gear. The transfer case had high and low gears, and engaged the front axle. Originally all axles were a Timken split type, later trucks also used GM "banjo" types. Chassis The CCKW had a ladder frame chassis with three driven beam axles, the front on leaf springs, the rear tandem on leaf springs with locating arms. There were two wheelbases, the short Model 352 and the long Model 353. The short, was used with a short cargo bed as an artillery prime mover for and howitzers. All other models used the long wheelbase. Tires were 7.50-20, brakes were hydraulic with vacuum assist. Some were fitted with front-mounted winches. A winch added and . Some open cab chassis were cut in half behind the cab for air transport. Each half was a load, at the vehicle's destination, the halves were bolted back together. ==Versions==
Versions
with M45 Quadmount on M20 trailer in bed, loading ramps attached to side Initially, all versions used a modified commercial AK series truck closed cab design having a metal roof and doors. By 1944, an open cab version, with a canvas roof and doors, was used. This was easier to build, and the roof could be removed to lower the shipping height. 1 in 4 of cabs had a machine gun mounting ring above the co-driver's position. The CCKW provided a platform for the widest range of bodies on any U.S. military vehicle, with the cargo version being the most common. As steel was more heavily rationed during the course of the war, the steel cargo bed was replaced by a wooden one. Wooden beds proved unsatisfactory and a 'composite' bed with steel sides, framing, and wooden bottom slats was developed. However, the composite bed was still unsatisfactory and the bed design returned to all steel. Standard cargo models had beds with fixed sides and a drop tailgate, as well as folding troop seats. A standard rectangular van configuration was used in communications, medical, workshop, and many other specialty roles. Special built vans were also used. Specialized variants Many specialized variants of the basic 6×6 CCKW were made, some in small numbers, including some converted in the field. These include: • Air compressor • Bomb service • Chemical decontaminating • Chemical handling • Dental operating van • Dump truck • Fire engine • Fuel & gas tankers () • Fuel & oil handling (), () • High lift • K-53 radio equip. van • K-60 radio equip. van • Map reproduction van • Ordnance maintenance van • Pipeline equipment • Ponton bolster • Semi-trailer tractor • Shop equipment GP repair van • Surgical van • Water purification van • Water tanker () • Welder's truck ACK-353 The ACK-353 (A for 1939 design, C for conventional cab, and K for all wheel drive) -ton 4×4 truck was the smaller brother of the ACKWX, and a predecessor to the Chevrolet G506, competing with the Dodge / Fargo T-203 / VF-400 series, as GM was at that time also trying to clinch the lucrative contract for the standard World War II cargo trucks in the -ton 4×4 category. The ACK-353 was equipped with the new for 1939 GMC 248 engine, an overhead valve, low-deck inline-six with a bore and stroke, resulting in a displacement, producing (net). The transmission was a four-speed manual, combined with a two-speed transfer-case engaging the front axle for all-wheel drive operation. The truck rode on a wheelbase, measuring long, wide, and tall – or with the rear top bows taken down. Some were kept in service by the Armistice Army ACKWX-353 The ACKWX-353 (A for 1939 design, C for conventional cab, K for all wheel drive, W for tandem rear axles, and X for non-standard chassis) three-ton 6x6 truck was the direct predecessor from which the CCKW was developed. Some 1,000 of the 3-ton 6x6 trucks were originally contracted by France, butjust like the 4×4 ACK trucksafter the defeat of the French, diverted to Britain in 1940. The British however, deemed the trucks unfavorable for use in the war, due to their long wheelbase and lacking power, and diverted them to the USSR in turn, in 1941. A total of 2,466 ACKWX trucks were built — both according to GMC's serial numbers, as well as the U.S. Army's acceptance figures. DUKW The DUKW (D for 1942 design, U for utility, K for all wheel drive, and W for tandem rear axles) — popularly the "Duck" – was an amphibious truck that shared the CCKW's driveline, but had a totally different body and structure than all the other trucks. First produced at Yellow's Pontiac plant, as demand increased production was added to Chevrolet's St. Louis plant. The hull, designed by an America's Cup winner, gave the truck respectable sea-keeping capability. A very successful design, 21,147 were built. ==Gallery==
Gallery
File:CCKW-rhine.jpg|80th Division crossing the Rhine near Mainz File:Convoy Red Ball Express.jpg|Red Ball Express convoy, 1944 File:G-508 6x6 GMC CCKW-353-2 Air Compressor truck pic1.JPG|Restored maintenance vehicle File:GMC Airportable3.JPG|Restored two part chassis for air transport ==See also==
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