M54 (truck)

The M54 Truck, officially designated Truck, Cargo, 5 Ton 6×6 M54, is a heavy cargo truck developed by, and deployed primarily with, the United States Armed Forces. The vehicle is a member of the M39 series of trucks. It is rated for five-ton cargo loads, cross-country, and ten-ton cargo loads, highway, making it a heavy truck. The basic M54 is fitted with a Continental gasoline engine, whereas variants had different engines (see below).

The vehicle is approximately 25 feet long and weighs approximately 10 tons when empty.

The M54 was the primary heavy truck of the U.S. Army and U.S. Marine forces during the Vietnam War. It was used to haul cargo, and was also modified to serve as a gun truck by adding armor and various weapons, including double, or Quadmount .50 caliber machine guns. The truck was also used by the U.S. Navy, and U.S. Air Force, and was deployed by ARVN forces in Vietnam as well.

Although most noted for its extensive use in Vietnam, the rugged, reliable M54 continues to serve in armed forces around the world to the present day.

Design and development
The M39 (a.k.a.G744) series was designed as a 5 ton three axle all wheel drive off road truck to replace World War II era trucks such as 4 and 6 ton 6x6’s built by Brockway, Diamond T, and White. Rushed into production by International Harvester in 1951, soon Kaiser (renamed Kaiser-Jeep in 1963) also became a major manufacturer, with Diamond T and Mack building smaller numbers. The M39 series evolved into the M809 (G908) series in 1969, which followed, but did not replace, it. The M809 Series was then improved into the M939 Series in 1983. Although individual components and dimensions may vary, all three series are mechanically very similar.

The M39 series were originally powered by a Continental R6602 gasoline engine, a 602 cubic inch inline 6 developing 224 gross horsepower at 2800 rpm. The -A1 upgrade had a Mack ENDT-673 turbocharged diesel engine with 210 hp. at 2100rpm. The -A2 had a Continental LDS-465-1A Turbo multifuel engine, with 205 hp. at 2600rpm. Later series have Cummins diesel engines. All M39s (excluding M139C/D/F) had a Spicer 5-speed manual transmission, 2-speed (plus forward and reverse) transfer case, and Timken axles with the same gear ratio, as did M809s as built. This drivetrain, designed for the Continental’s 2800rpm. governed speed, was poorly suited for the multifuel and diesel’s lower operating ranges. The M939 series automatic transmissions have addressed this issue.

The M39 series were built on chassis with three wheelbases, and designed with single or dual rear tires. The M39 chassis, namesake of the series, was a single rear tire model, few were built. Virtually all trucks were built on dual rear tire chassis, the M40 long(179”/206”) wheelbase, used in the basic M54, the M61 short(167”/194”) wheelbase, used in semi tractors and dump trucks, and the M63 extra long(215”/242”) wheelbase, used in the M55. There was also an oversize M139 chassis for extreme service.

Cargo variants
There were two main variants of the cargo truck, the standard M54 with a 14’ long flatbed cargo body and the M55 model on an extra long wheelbase with a 20’ body. The M54 was modified to serve as a dropside cargo vehicle as well, these being designated M54A1C and M54A2C. Service variations existed as well, notable was the tall intake on the air cleaner of M54s deployed by the U.S. Marine Corps.

Tractor and Wrecker variants
Only one semi tractor model was developed, the M52. The first model wrecker was the M62, succeeded by the M543, with a different boom. The M246, with a XL wheelbase, was a wrecker/tractor, with a fifth wheel mounted behind the boom, for towing semi trailers.

Construction variants
M39 series trucks were used widely in construction, often for river bridging, and a number of specialized construction variants were developed. The M51 dump truck was developed for general construction work, while the M139, M328, and M748 were used to deliver large sections of bridging material.

Expansible vans
The M291 Expansible van, on an XL wheelbase with a slide out section on each side, had a large working floor area and was used in communication roles. Some had hydraulic lift gates.

Chassis cabs
In addition to standardized models, bare chassis cabs were produced for specialty bodies. Possibly the most extreme were the M139C, D, and F, with heavier front axles and lower gear ratios, used for missile launchers.

Operators

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