Diamond T

Commercial models

1928–1929 brought major mechanical improvements across the entire range. A closed cab with doors was introduced. All-wheel hydraulic drum brakes were used. Six-cylinder engines were available from Continental and Hercules for heavy trucks and a four-cylinder Buda powered light trucks. All trucks had geared-differential rear axles. By 1929 there were chassis load ratings (the weight of the body and payload) up to 12 tons (10,900 kg) on three axles.

1933–1935 In 1933 a new all-steel covered cab with doors and roll-up windows was introduced. In a 1935 model year style change it had been improved with a "streamlined" V-style windshield. This cab would be used on commercial and military trucks until replaced in 1951. In 1935 the trucks were also improved mechanically and new models were introduced. They developed through the rest of the 1930s. In 1935, Diamond T sold 6454 units and in 1936 it increased to 8750 trucks.^[8] In 1938, Diamond T sold 4393 units and in 1939 it increased to 5412 trucks.^[9] In 1940 Hercules six-cylinder gasoline and diesel engines up to 118 horsepower (88 kW) were used and Cummins diesels up to 200 horsepower (150 kW) were introduced in 1940.

1940–1942 In 1940 Hercules six-cylinder gasoline and diesel engines up to 118 horsepower (88 kW) were used and Cummins diesels up to 200 horsepower (150 kW) were introduced. In 1942 improved models went into production and then stopped after only 530 units for military production of tactical trucks and half-tracks.

1946–1947 Production of commercial trucks was stopped for military production in 1942. A small number of commercial trucks began to be built in 1944 and more in 1945. In 1946, the first year of full commercial production, there were five models, in 1947 there were fourteen. After World War II heavy trucks were measured by Gross Vehicle Weight Rating (GVWR), the total weight of the chassis, body, and payload. In 1947 there were chassis rated from 8,000 pounds (3,600 kg) to 36,000 pounds (16,000 kg) with conventional, sleeper, and COE models. Annual model changes were discontinued and many models continued unchanged until 1950. Gasoline and diesel engines were offered by Continental, Cummins, and Hercules. Single and tandem rear axles were available in many wheelbases.

Military models

Model 980/981 12-ton 6x4 trucks (G159) were ballast tractors used as tank transporters. Designed for the British military they were also used by the US Army. Powered by a 895 cubic inches (14.7 L) Hercules DFXE diesel engine developing 185 horsepower (138 kW) and geared very low, it could pull a trailer of up to 115,000 pounds (52,000 kg) and proved capable of the task of moving the heaviest tanks then in service. Early trucks used a standard Diamond T commercial cab (also used by the 4-ton G509 trucks). In August 1943 it was replaced with an open military cab. A long butterfly hood had vertical louvers along both sides.^[3][10]

A short ballast body was mounted behind a mid-mounted winch. There were closed tool compartments along both sides, two open containers in the front, and a bottom-hinged tailgate. The box could hold 18,000 pounds (8,200 kg) of ballast to increase traction on the rear tandem axles. When paired with the M9 Rogers trailer, the combination was designated the M19 tank transporter.^[3][10] A number of cars were delivered to the USSR under Lend-Lease during WWII.

Model 968 4-ton 6x6 truck (G509) Prime mover cargo trucks entered production as the standard 4-ton 6x6 chassis in 1941. It was produced with both a closed steel commercial-style cab and later an open military cab. It was designed to tow the 155 mm howitzer and carry its crew and ammunition. The chassis was used for different bodies, but the majority of 4-tons were Model 968s.^[4][11]

Standard models were powered by the 6 cyl., 529 cubic inches (8.7 L) Hercules RXC engine that developed 106 horsepower (79 kW) mated to a five speed manual transmission and two speed transfer case. The truck weighed 18,450 pounds (8,370 kg) and could tow 25,000 pounds (11,000 kg).^[4][11]

Model 967 was a pre-standard prime mover cargo truck (21 were built as wreckers). Produced in early 1941, it was fitted with Hercules RXB 501 cubic inches (8.2 L) inline six cylinder engine. Distinguishable by one piece brush guard on the front.^[4]

Model 969 Wrecker was the US Army's standard medium wrecker during World War II. It was equipped with the Holmes W-45 heavy-duty military wrecker bed with its twin boom and two 5-ton winches at the front of the bed as well as a front-mounted winch. A variety of other recovery equipment was carried, along with its own air compressor. It weighed 21,350 pounds (9,680 kg) and could tow 25,000 pounds (11,000 kg).^[4]

Model 970 Cargo truck was designed to carry bridging pontoons. The bed is 16 inches (406.40 mm) longer than the 968.^[4]

Model 972 dump truck was the largest dump truck the US Army had during World War II. Originally they were not fitted with front winches in order to reduce front axle loading. After a Corps of Engineers request, winches were fitted from June 1944 onwards.^[4]

Model 975 was a bridge truck built for Canada.