The name CCKW comes from GMC model nomenclature:  In 1939-1940 the US Army Ordnance Corps was developing -ton (2,268 kg) load-rated 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 ACKWX – built for the French Army – into 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. 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 6x6 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. acceptances 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 of -ton, 6-wheeled trucks that was second only to the WW II “Jeep” — and neither Ford nor Willys individually built as many jeeps during the war. The CCKW was equipped with the GMC 270 engine, an overhead valve inline-6 with or at 2750rpm, and at 1400rpm. A bore by stroke gave a displacement. This (gasoline) engine was designed for commercial trucks, and was reliable in service.