1. Etymology

The name CCKW comes from GMC model nomenclature:^[1]

• "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 ^[2])

2. History

In 1939-1940 the US Army Ordnance Corps was developing ​2 ¹⁄₂-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.^[3] 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.^[4][5]

3. 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 ​2 ¹⁄₂-ton 6x6 units (excluding the DUKW) produced by GMC — versus a total of 527,168 accepted by the U.S. Army.^[2] Jackson's tabulation of the 1946 U.S. acceptances numbers adds up to 524,873 units, excluding the DUKWs and the ACKWX predecessor models.^[6][7] 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.^[2][6] 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.^[2]

In any case, GM / GMC built a total of ​2 ¹⁄₂-ton, 6-wheeled trucks that was second only to the WW II “Jeep” ^[3] — and neither Ford nor Willys individually built as many jeeps during the war.

4. Specifications

4.1. Engine and Drive-Line

The CCKW was equipped with the GMC 270 engine, an overhead valve inline-6 with 91.5 hp (68.2 kW) ^[8] or 104 hp (78 kW) ^[9] at 2750rpm, and 216 pound-feet (293 N⋅m) at 1400rpm.^[8] A 3 ²⁵⁄₃₂ in (96 mm) bore by 4 in (102 mm) stroke gave a 269.5 cu in (4.4 L) displacement.^[10] This (gasoline) engine was designed for commercial trucks, and was reliable in service.^[11]

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.^[12][13]

4.2. 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, 145 in (368 cm) (Measurements are from the centerline of the front axle to the centerline of rear bogie) was used with a short cargo bed as an artillery prime mover for 75 mm and 105 mm howitzers. All other models used the long 164 in (417 cm) wheelbase. Tires were 7.50-20, brakes were hydraulic with vacuum assist.^[11]

Some were fitted with 10,000 lb (4,500 kg) front-mounted winches. A winch added 300 pounds (140 kg) and 14 inches (36 cm).^[14]

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.^[11][15]

5. Versions

Van body with canvas roof and doors in place. https://handwiki.org/wiki/index.php?curid=1807514

Gasoline tanker (750 US gal (2,800 l)). https://handwiki.org/wiki/index.php?curid=1140302

CCKW-353-B2 gun truck with M45 Quadmount on M20 trailer in bed, loading ramps attached to side. https://handwiki.org/wiki/index.php?curid=1577334

Initially, all versions used a modified commercial 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.^[11]

The CCKW provided a platform for the widest range of bodies on any U.S. military vehicle, with the 12 ft (3.7 m) 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.^[5] 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.^[16]

5.1. 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:^[17]

• Air compressor
• Bomb service
• Chemical decontaminating
• Chemical handling
• Dental operating van
• Dump truck
• Fire engine
• Fuel & gas tankers (750 US gal (2,800 l))
• Fuel & oil handling (660 US gal (2,500 l)), (750 US gal (2,800 l))
• 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^[18]
• Shop equipment GP repair van
• Surgical van
• Water purification van
• Water tanker (700 US gal (2,600 l))
• Welder's truck

5.2. ACK-353

The ACK-353 (A for 1939 design, C for conventional cab, and K for all wheel drive) ​1 ¹⁄₂-ton 4x4 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 4x4 category.^[19]

The ACK-353 was equipped with the new for 1939 GMC 248 engine, an overhead valve, low-deck inline-six with a 3 ²³⁄₃₂ in (94 mm) bore and 3 ¹³⁄₁₆ in (97 mm) stroke, resulting in a 248 cu in (4.1 L) displacement, producing 77 brake horsepower (57 kW) (net).^[20][21] Transmission was four-speed manual, combined with a two-speed transfer-case engaging the front axle for all-wheel drive operation.

The truck rode on a 157 ³⁄₄ in (401 cm) wheelbase, measuring 256 in (650 cm) long, 90 in (229 cm) wide, and 117 in (297 cm) tall – or 89 in (226 cm) with the rear top bows taken down.^[21] Tires were 7.50-20, and weight came in at 7,532 lb (3,416 kg). 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,^[21] although some 2,000 units delivered to the French in early 1940 likely fell into the hands of the Nazi Germany Wehrmacht.^[22]

5.3. 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.^[23] Fitted with the same 77 brake horsepower (57 kW) drivetrain as the ACK, the trucks weighed 9,856 lb (4,471 kg), and measured 264 in (671 cm) long, 94.5 in (240 cm) wide, and 118 in (300 cm) tall / or 90 in (229 cm) to cab.^[24]

GMC AFKWX-353 cab-over-engine. https://handwiki.org/wiki/index.php?curid=1556719

Some 1,000 of the 3-ton 6x6 trucks were originally contracted by France, but – just like the 4x4 ACK trucks – after 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 Russia in turn, in 1941.^[23] 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.^[2]

5.4. AFKWX-353

The AFKWX (A for 1939 design, F for forward cab, K for all wheel drive, W for tandem rear axles, and X for non-standard chassis) 353, a cab over engine, long cargo bed version of the CCKW, went into production alongside it in 1942 at Yellow’s Pontiac plant and Chevrolet’s in St. Louis. Otherwise mechanically identical, its compact cabin design allowed a 15 ft (4.57 m), and later 17 ft (5.18 m) cargo bed to be fitted. Only the first 50 units produced had closed cabs, all others were open. None had a front-mounted winch. The cab over design made engine maintenance difficult. As a result, only 7,235 were built,^[25][26] – 2,232 units with the 15 ft. body, and 5,000 of the 17 ft. version.^[6]

DUKW in use by American troops in France. https://handwiki.org/wiki/index.php?curid=1148793

5.5. CCW-353

The CCW-353 (C for 1941 design, C for conventional cab, and W for tandem rear axles) was a near identical version of the CCKW-353, that lacked its front-wheel drive, resulting in an officially purely on-road, and therefore 5-ton rated, 6×4 version of the same truck. A beam front axle was used, with the transfer case locked in high range. Of the ~118,000 ​2 ¹⁄₂-ton, 6x4 trucks the U.S. built in WW II, GMC contributed 23,649 units of the CCW-353 as standard cargo trucks without winch – almost all of them built in 1942.^[27]

5.6. 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.^[28][29][30]