09/18/2026
The four trucks represent a remarkable progression in American military logistics: the 1942 GMC CCKW was a World War II-era 2½-ton workhorse built around simplicity and mass production, the 1952 M35 refined that same basic tactical-truck concept with a more modern chassis and drivetrain, the 1983 M939 moved into the 5-ton class with substantially greater payload and a more powerful diesel powertrain, while the Oshkosh HEMTT M977 represented a completely different generation of heavy tactical mobility, with 8×8 drive, roughly 10-ton payload capability, and much greater off-road carrying capacity.
The 1942 GMC CCKW 6×6 was the oldest and mechanically simplest truck here. Its GMC 270 was a 4.4-liter overhead-valve gasoline inline-six producing about 104 hp and 216 lb-ft of torque, although some references give a lower 91.5-hp rating depending on specification. It used a five-speed manual transmission with a two-range transfer case, allowing the front axle to be engaged for six-wheel drive. The chassis used three driven beam axles with leaf springs, while braking was hydraulic with vacuum assistance. A typical CCKW 353 weighed about 8,800 lb empty and 16,400 lb loaded, with a rated 2½-ton cargo capacity. Its maximum road speed was only around 45 mph and its operational range was approximately 300 miles.
What makes the CCKW impressive is not its raw performance but how effectively those modest specifications were turned into a military logistics system. The truck was designed around the idea that thousands of relatively simple vehicles could keep an army supplied across poor roads, mud, fields and damaged infrastructure. The 6×6 drivetrain, low-range transfer case, high ground clearance and flexible leaf-spring suspension gave it considerably better off-road mobility than a normal civilian truck of the early 1940s. It could carry am******on, fuel, food, troops, engineering equipment and artillery-related loads. Some versions also received a roughly 10,000-lb front winch.
The biggest limitation was the gasoline powertrain. Around 104 hp moving a fully loaded vehicle of roughly 16,400 lb means the CCKW had a very modest power-to-weight ratio by later military-truck standards. It was not designed for rapid acceleration or high-speed highway transportation. Its strength was controlled, low-speed movement over difficult terrain. Steering was manual-era heavy-truck equipment, braking technology was considerably more primitive than what came later, and the driver worked with a much noisier, less comfortable cab. Nevertheless, the CCKW established the basic American tactical cargo-truck formula that the M35 would later refine.
The 1952 M35 2½-ton 6×6 was essentially the next major step in that evolution. The M35 originated from REO's postwar design and entered service around 1949, with the 1952 period falling within the early M35/M35A1 generation. Unlike the CCKW's gasoline engine, early M35 trucks used the REO OA-331 gasoline engine, producing about 127 hp. It employed a five-speed transmission with a two-range transfer case and retained the 6×6 configuration. The basic truck weighed roughly 14,880 lb empty and around 17,880 lb loaded in one commonly cited configuration.
The M35's significance is that it did not simply increase engine output; it modernized the entire tactical-truck concept. Its chassis was designed for better serviceability, durability and versatility, and the M35 family eventually became a huge platform for cargo bodies, fuel tankers, dump bodies, troop carriers and specialized equipment. The basic M35 was rated for about 5,000 lb off-road and could carry substantially more on roads under appropriate conditions.
Compared directly with the CCKW, the M35 feels like a much more mature military vehicle. The CCKW is a World War II logistics machine optimized for mass wartime production; the M35 was designed for a longer service life and a broader range of postwar missions. The M35 still used beam axles and leaf springs, so it retained the rugged mechanical philosophy of the earlier truck, but its chassis, cab, drivetrain and cargo system were more refined. The M35 also became famous for its later diesel-powered M35A2 configuration, which dramatically improved fuel economy, range and low-speed pulling characteristics compared with the original gasoline trucks. It is important, however, not to apply the later M35A2 diesel specifications to a 1952 truck.
Then the 1983 M939 5-ton 6×6 represents a much larger jump in capability. The M939 family was introduced in 1983 as an improvement of the earlier M809-series 5-ton trucks. It was designed to carry a 10,000-lb cargo load across all terrain, effectively doubling the nominal off-road cargo capacity of the 2½-ton class represented by the CCKW and M35.
Early M939/M939A1 vehicles used the Cummins NHC-250 14-liter naturally aspirated inline-six diesel, rated at approximately 240 hp and 685 lb-ft of torque. Later M939A2 models received the Cummins 6CTA8.3, so it is important not to mix A2 specifications into an early 1983 example. The M939 used an automatic transmission with a two-range transfer case, rather than the manual gearbox philosophy of the earlier 2½-ton trucks.
That automatic transmission is a major operational difference. The driver no longer had to manually manage a heavy clutch and gear lever while simultaneously dealing with mud, steep grades and changing terrain. The automatic drivetrain made the truck easier to operate under battlefield conditions and allowed the engine to remain closer to its useful torque range. The M939 still retained heavy beam axles and leaf-spring suspension, emphasizing durability and load carrying rather than civilian-style ride comfort.
Its 5-ton rating also changes the entire logistical role. An M35 could carry am******on, personnel and supplies for a relatively mobile tactical formation. An M939 could move much larger quantities of am******on, engineering material, artillery equipment and other heavy loads while still retaining 6×6 off-road capability. The family also included cargo trucks, dump trucks, tractor units, wreckers and other specialized configurations. Approximately 44,590 vehicles were produced by AM General, with additional production and derivatives outside the original U.S. production run.
The Oshkosh HEMTT M977 is where the comparison changes dramatically. One correction is important: the HEMTT family entered U.S. Army service in 1982, not 1999. The year 1999 can refer to particular HEMTT variants or production periods, but the M977 itself was already an established HEMTT model by then. The original HEMTT M977 was an 8×8 heavy tactical cargo truck designed around the Army's requirement for substantially greater mobility and payload than the preceding 5-ton class.
The early M977 used a Detroit Diesel 8V92TA 14.0-liter two-stroke V8 producing approximately 445 hp, coupled to an Allison HT740D automatic transmission. The truck used an Oshkosh two-speed transfer case and 8×8 drive. Its original M977 specification listed a 62,000-lb GVWR, 100,000-lb GCWR, an approximately 22,000-lb payload capability, and a cargo body around 18 feet long.
This makes the HEMTT dramatically different from the CCKW and M35. It is not simply a larger version of the same truck. The forward-control cab places the driver ahead of the engine, the vehicle has four axles rather than three, and all eight wheels are driven. Ground clearance is around 24 inches, maximum grade capability is approximately 60 percent under specified conditions, and maximum road speed is around 55-57 mph. Published specifications also give an approximate 300-mile range.
Its suspension and axle arrangement are designed around heavy loads and cross-country mobility. The original HEMTT uses Hendrickson-type equalizing-beam suspension with substantial vertical travel, allowing the four axles to remain in contact with uneven terrain while distributing load across the chassis. That is one of the reasons an HEMTT can carry a much heavier payload while maintaining tactical mobility.
The HEMTT also introduced a much more sophisticated approach to military logistics. The M977 cargo version was only one member of a family that included the M978 fuel tanker, M983 tractor, M984 wrecker and M985 cargo vehicle. The common chassis concept allowed the Army to build a family of specialized heavy logistical vehicles instead of developing completely different platforms for every mission.
In raw power, the progression is enormous. The CCKW's roughly 104 hp gasoline six-cylinder engine is tiny compared with the M35's approximately 127 hp early gasoline engine. The M939 then moves to approximately 240 hp and nearly 685 lb-ft in its early diesel configuration. The original HEMTT M977 jumps to roughly 445 hp. That means the HEMTT has more than four times the horsepower of the CCKW while carrying a payload many times greater.
The difference in drivetrain philosophy is equally important. The CCKW and early M35 are fundamentally mechanical, manual-transmission trucks. They require more driver involvement and rely heavily on mechanical simplicity. The M939 introduces an automatic transmission into the 5-ton class, while the HEMTT takes that concept considerably further with a powerful diesel, automatic transmission, two-speed transfer case and an 8×8 drivetrain. The result is much easier heavy-load operation and far greater ability to maintain mobility when the vehicle is carrying a substantial payload.
Off-road, the CCKW was revolutionary for its era, but the HEMTT operates on an entirely different level. The CCKW's three axles and 6×6 configuration were excellent for 1940s battlefield logistics. The M35 refined this arrangement. The M939 increased axle and chassis capacity while retaining 6×6 mobility. The HEMTT adds a fourth driven axle, larger tires, greater ground clearance, much more engine torque and a chassis specifically engineered around heavy tactical loads. Its purpose is not simply to get a load from one road to another; it is to keep very heavy logistical equipment moving through terrain that would challenge conventional trucks.
Braking also shows the technological progression. The CCKW relied on hydraulic brakes with vacuum assistance, appropriate for its era. Later vehicles increasingly used heavy-duty air braking systems. The HEMTT's braking system was designed for a vehicle with vastly greater mass and payload, and the original specification lists air-operated heavy-truck braking equipment.
Cab comfort follows the same trajectory. The CCKW's cab is extremely basic by modern standards, with minimal insulation, primitive instrumentation and little concern for driver comfort beyond what was necessary for wartime service. The M35 improved the basic environment and became famous for its utilitarian but serviceable cab. The M939 continued that philosophy with a larger heavy-truck platform. The HEMTT, despite remaining a military vehicle, was designed around longer-duration heavy logistical missions and provided a substantially more capable cab and control environment. Later HEMTT generations went much further with improved climate control, armor compatibility and modernized driver protection.
For pure historical significance, the CCKW is the foundation of this group. It demonstrated how standardized 6×6 trucks could transform military logistics during World War II. For the classic 2½-ton tactical-truck concept, the M35 is the more mature evolution, taking the basic "deuce-and-a-half" formula into the postwar era. For traditional 5-ton cargo transportation, the M939 is a major step upward in payload and drivetrain sophistication. For extreme heavy tactical logistics, the HEMTT is in another class entirely.
The CCKW is therefore best understood as a World War II mass-logistics workhorse. The M35 is the long-service 2½-ton tactical successor. The M939 is the heavy 5-ton all-terrain logistics platform. The HEMTT M977 is the heavy 8×8 tactical logistics machine designed to move substantially larger loads while retaining battlefield mobility.
The most interesting part of the evolution is that the trucks did not simply become "bigger." Their missions changed with them. The CCKW proved the value of standardized 6×6 mobility. The M35 made that concept more durable and adaptable. The M939 increased payload and reduced driver workload through diesel power and automatic transmission. The HEMTT finally moved the American tactical cargo truck into a heavy 8×8 architecture capable of carrying loads that would have been completely outside the design envelope of the original CCKW.
