The GMC CCKW, also known as "Jimmy", or the G-508 by its Ordnance Supply Catalog number,[a] was a highly successful series of off-road capable, 21⁄2-ton, 6×6 trucks, built in large numbers to a standardized design (from 1941 to 1945) 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 famed Red Ball Express that kept Allied armies supplied as they pushed eastward after the Normandy invasion.

GMC's total of ~550,000 purely 6×6 models, including the DUKW, formed the overwhelming majority of the ~675,000 six by six 2+1⁄2-ton trucks, and came in less than 100,000 shy of the almost 650,000 World War II jeeps.

Eventually, the M35 series, originally developed by REO Motors, succeeded the CCKW as the U.S. Army's standard 2+1⁄2-ton, 6×6 cargo truck.

[9] 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.

Ware (2010)[citation needed] lists one single number of 562,750 of CCKW trucks, built across all variants—presumably including the amphibian DUKW.

[6] Jackson's tabulation of the 1946 U.S. acceptance numbers adds up to 524,873 units, excluding the DUKWs and the ACKWX predecessor models.

[6][7] 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.

[14] The CCKW provided a platform for the widest range of bodies on any U.S. military vehicle,[citation needed] with the 12 ft (3.7 m) cargo version being the most common.

Standard cargo models had beds with fixed sides and a drop tailgate, as well as folding troop seats.

These include:[20] The ACK-353 (A for 1939 design, C for conventional cab, and K for all wheel drive) 1+1⁄2-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 1+1⁄2-ton 4×4 category.

[23][24] The transmission was a four-speed manual, combined with a two-speed transfer-case engaging the front axle for all-wheel drive operation.

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,[24] 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.

[26] 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.

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.