This page continues the description of U.S. WW II 2 1/2-ton, 6x6 trucks with details of the GMC CCKW, the Studebaker & Reo US-6, and the International Harvester M-5H-6. All of these trucks had the same general description as 2 1/2-ton, 6x6 trucks, but differed in many details of construction and operation.
The General Motors Corporation Truck, 2 1/2-ton, 6x6, Cargo, CCKW (G-508) was named according the GMC production nomenclature of the time. CCKW was assigned by GMC using their standard system as follows: C = designed in 1941, C = standard cab, K = front wheel drive, W = rear wheel drive. GMC production of the CCKW began in 1941 and ended in 1945, with a total of 562,750 manufactured, the most commonly used tactical vehicle in World War II. It remained in service until 1956, including use in the Korean War.
CCKWs were originally fitted with a sheet metal cab (called the "closed cab"), but after July 1943 a canvas cab was substituted to save steel and reduce shipping volume (the "open cab"). Both long (164 in. CCKW-353) and short (145 in. CCKW-352) wheelbase models were produced, as well as numerous variations on body style and running gear.
The CCKW had the 92hp GMC 270 6 cal. engine. The weight was 10,350 lbs. (CCKW-352) or 11,250 lbs. (CCKW-353). Width was 86.25 inches and height 93 inches.
The basic cargo truck had folding troop seats in the bed. Other body variations included:
Airfield service (750 gal. tank)
M27 or M27B1 Bomb Service
Shop van (ST-5 and ST-6 body)
Tanker, fuel (twin 350 gal. tanks)
The van body and shelter carriers could be configured for many purposes. The short wheelbase version of the CCKW was identified by the code 352, indicating a 145 inch wheelbase, intended primarily for towing artillery. The code 353 meant the long wheelbase version with a 164 inch wheelbase, intended for moving cargo and personnel. There were two types of axle, the Timken split axle and the GMC banjo type axle, indicated by a "1" or "2" respectively as the truck type suffix. The CCKW could be equipped with a GarWood (2-U512) or Heil (JJ-104-B, 125G or 125G1) 10,000 lb. PTO winch, but only if the front frame and bumper were factory-built for it.
A system of letter codes was used for the CCKW body types. This list is some of the most common:
A Cargo body w/o winch
B Cargo body w/ winch
C Stake wagon
D Gasoline tanker w/o winch
E Gasoline tanker w/ winch
F Van body
G Water tanker w/o winch
H Dump w/ winch
L Dump w/o winch
ST5/ST6 Workshop w/o winch
CCKW trucks could be fully described by a combination of the codes. For example, "CCKW 353 E2" indicates a long wheelbase gas tanker w/winch and the banjo axle.
Studebaker & Reo US-6 (G-630)
Although the CCKW was the most numerous of the WW II 2 1/2 ton, 6x6 cargo trucks, almost 200,000 of the Studebaker-designed US-6 (G-630) were produced by Studebaker and another 22,000 by Reo from 1941-45. Their engine was the 6 cal. 320cid Hercules JXD, mated with GMC transfer case, GMC transmission, and Timken split design axles as used on the CCKW. Most of these trucks were built with a closed, metal cab since they were primarily shipped to the Soviet Union under Lend Lease. The trucks were produced in short and long wheelbase with many of the CCKW body types mounted on the US6 chassis, but primarily the cargo body. A 6x4 US6 version with an undriven front axle was also produced in three versions: a tractor plus long and short wheelbase cargo trucks.
The US6 and CCKW are very similar externally, but the position of the gas tank is on the driver's side of the US6 vs. on the passenger side of the CCKW-353. The US6 had no louvers on the sides of the engine compartment, while both the IH M-5H-6 and the GMC CCKW did have louver slots.
International Harvester M-5H-6 (G-651)
The International Harvester M-5H-6 (G-651) was intended to be equivalent to the CCKW and US6 2 1/2 ton, 6x6 trucks for military purposes. It was used almost exclusively by the U.S. Navy and Marine Corps during WW II. Although quite similar in function and appearance, there are many small differences. To distinguish the M-5H-6, the visual clues are a one piece windshield and about two dozen louvered ventilation slits in the engine compartment side panels (vs twelve on the CCKW and none on the US6).
More significant for military operations, the M-5H-6 rear end had the Hendrickson walking beam suspension and Thornton locking differentials making this truck a much better off-road performer than its deuce cousins, vital for the Marines when they encountered beaches and bogs all over the Pacific Theater in WW II.
Body variants included:
Cargo (long 169 in. and short 149 in. wheelbase)
Dump (short 149 in. wheelbase)
Early production was called the M-5-6. They were all soft top but otherwise the same as the M-5H-6.