The M425 and M426 Tractor trucks ( G671) were 5 ton (4,536kg) load rated 4x2 semi-tractors that were used from 1944 on by the US Army. They are famous for the use on the

Red Ball Express The Red Ball Express was a famed truck convoy system that supplied Allied forces moving quickly through Europe after breaking out from the D-Day beaches in Normandy in 1944. To expedite cargo shipment to the front, trucks emblazoned with red ...

from Normandy to the front, but were also used in the

China Burma India Theater China Burma India Theater (CBI) was the United States military designation during World War II for the China and Southeast Asian or India–Burma (IBT) theaters. Operational command of Allied forces (including U.S. forces) in the CBI was officia ...

. After the war they were used in Europe, including during the Berlin Crisis, and in the

Korean War , date = {{Ubl, 25 June 1950 – 27 July 1953 (''de facto'')({{Age in years, months, weeks and days, month1=6, day1=25, year1=1950, month2=7, day2=27, year2=1953), 25 June 1950 – present (''de jure'')({{Age in years, months, weeks a ...

History

Designed and first manufactured by

International Harvester The International Harvester Company (often abbreviated by IHC, IH, or simply International ( colloq.)) was an American manufacturer of agricultural and construction equipment, automobiles, commercial trucks, lawn and garden products, household e ...

, later

Kenworth Kenworth Truck Company is an American truck manufacturer. Founded in 1923 as the successor to Gersix Motor Company, Kenworth specializes in production of heavy-duty ( Class 8) and medium-duty (Class 5–7) commercial vehicles. Headquartered in ...

and

Marmon-Herrington The Marmon-Herrington Company, Inc. is an American manufacturer of axles and transfer cases for trucks and other vehicles. Earlier, the company built military vehicles and some tanks during World War II, and until the late 1950s or early 1960s wa ...

also built them. The official model number was 542, to which are added a prefix letter designating the manufacturer of the engine (thus 'H' from Harvester) and a suffix number relating to the tire size. The M426 was a heavier duty evolution of the M425. All model H-542-9 M425s were built by International, H542-11 M426s were built by all three companies. 1,200 M425s were upgraded to M426 standards.

Engine and driveline

The engine in these vehicles was an International Red Diamond 450D, a

overhead valve An overhead valve (OHV) engine, sometimes called a ''pushrod engine'', is a piston engine whose valves are located in the cylinder head above the combustion chamber. This contrasts with earlier flathead engines, where the valves were located be ...

inline 6 cylinder

gasoline engine A petrol engine (gasoline engine in American English) is an internal combustion engine designed to run on petrol (gasoline). Petrol engines can often be adapted to also run on fuels such as liquefied petroleum gas and ethanol blends (such as ''E ...

developing at 2700

rpm Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or with the notation min−1) is a unit of rotational speed or rotational frequency for rotating machines. Standards ISO 80000-3:2019 defines a unit of rotation as the dimensionl ...

. The clutch was made by W.C. Lips, Model Z-32-S, and the

transmission Transmission may refer to: Medicine, science and technology * Power transmission ** Electric power transmission ** Propulsion transmission, technology allowing controlled application of power *** Automatic transmission *** Manual transmission *** ...

was an IHC Model F-54-D. This transmission had 5 forward and one reverse speed. The first speed was very low, fifth speed was direct.

Chassis

All models had a

ladder frame A vehicle frame, also historically known as its ''chassis'', is the main supporting structure of a motor vehicle to which all other components are attached, comparable to the skeleton of an organism. Until the 1930s, virtually every car had a ...

with two axles on semi elliptical

leaf springs A leaf spring is a simple form of spring commonly used for the suspension in wheeled vehicles. Originally called a ''laminated'' or ''carriage spring'', and sometimes referred to as a semi-elliptical spring, elliptical spring, or cart spring, ...

. A set back front axle allowed a

wheelbase In both road and rail vehicles, the wheelbase is the horizontal distance between the centers of the front and rear wheels. For road vehicles with more than two axles (e.g. some trucks), the wheelbase is the distance between the steering (front ...

of only , allowing a very short turn radius. The M425 and M426 were general service load carriers, designed to haul load over roads, so they didn't need to be 4 x 4. The front axle was an I-beam, the rear was a double reduction full floating type. International used their own front and rear axles, Kenworth and Marmon-Herrington used Timkens. Brakes were full air with

drum brakes A drum brake is a brake that uses friction caused by a set of shoes or pads that press outward against a rotating cylinder-shaped part called a brake drum. The term ''drum brake'' usually means a brake in which shoes press on the inner surfac ...

on all wheels. Trailer brakes could be used independently of the tractor. A disk type hand brake was mounted on the propeller shaft. M425s had 9.00x20 size tires, while M426s had larger 11.00x20s with stronger springs and a slightly longer wheelbase. All had dual rear tires. Except for the difference in the size of the tires, and some minor details, all types are mechanically identical. All models were a

cab over engine Cab-over, also known as cab over engine (COE), cab forward (U.S.), flat nose (Canada), or forward control (UK), is a body style of truck, bus, or van that has a vertical front, "flat face" or a semi-hood, with the cab of the truck sitting ab ...

design with a military style open cab.

Trailers

The M425 towed a 7-ton (6,350kg) load rated trailer long, the M426 a 10-ton (9,072kg) trailer long. Both had a single axle with dual rear tires, and a stake-and-platform body.

Gallery

File:M425 and M426.1.jpg, M425 with roof and doors File:M425 and M426.2.jpg, M425 with roof and doors File:US 7 ton trailer.jpg, 7 ton trailer File:US 10 ton trailer.jpg, 10 ton trailer

References

* * {{WWII US Soft Vehicles International Harvester vehicles Kenworth vehicles Military trucks of the United States Vehicles introduced in 1944 Marmon-Herrington vehicles