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, 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.
The CCKW came in many variants, including open or closed cab, long wheelbase CCKW-353 and short CCKW-352, and over a score of specialized models, but the bulk were standard, general purpose, cargo models. A large minority were built with a front mounted winch, and one in four of the cabs had a machine-gun mounting ring above the co-driver's position.
Of the almost 2.4 million trucks that the U.S. Army bought between 1939 and December 1945, across all payload weight classes, some 812,000, or just over one third, were -ton trucks. GMC's total production of the CCKW and its variants, including the 2-ton, 6x6, amphibian DUKW, and the 6×4, 5-ton CCW-353, amounted to some 572,500 units – almost a quarter of the total WW II U.S. truck production, and 70 percent of the total -ton trucks. GMC's total of ~550,000 purely 6×6 models, including the DUKW, formed the overwhelming majority of the ~675,000 six by six -ton trucks, and came in less than 100,000 shy of the almost 650,000 World War II jeeps. Additionally, GM built over 150,000 units of the CCKW's smaller brother, the -ton, 4×4 Chevrolet G506, at the same factory.
The GMC CCKW began to be phased out once the M35 series trucks were first deployed in the 1950s, but remained in active U.S. service until the mid-1960s. Eventually, the M35 series, originally developed by REO Motors, succeeded the CCKW as the U.S. Army's standard -ton, 6×6 cargo truck.
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
History
Production numbers
Sources do not precisely agree on the total numbers of CCKWs built by the end of production in 1945. Ware 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 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
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
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 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 . 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. Tires were 7.50-20, and weight came in at. A special feature were the front hubs, designed to take dual wheels in especially challenging terrain.
Fitted with steel GS bodies with fixed sides and troop seats, the trucks were originally ordered under French contract, but ended up in use by the British Army, although some 2,000 units delivered to the French in early 1940 were used from June 1940 to reequip the infantry of the light mechanized divisions whose equipment had been lost at Dunkirk. Some were kept in service by the Armistice Army and others likely fell into the hands of the Nazi Germany Wehrmacht.
ACKWX-353
The ACKWX-353 three-ton 6x6 truck was the direct predecessor from which the CCKW was developed. Fitted with the same drivetrain as the ACK, the trucks weighed, and measured long, wide, and tall / or to cab.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.