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Tractor Trendsetters: Farmall Super M-TA

Oct 03, 2011

Written by Larry Gay

The earliest farm tractors were built with transmissions that provided one speed forward and one speed in reverse. Then, as tractors began to be used for field work, the manufacturers added a second forward speed. Hart-Parr advertised that its speeds of 2 and 3 miles per hour provided the proper speed for plowing and the flexibility for other tasks. Many of the new tractor models introduced during the 1920s were equipped with three-speed transmissions.
Rubber tires for tractors were introduced in the fall of 1932 and farmers soon requested a faster speed for transportation on the roads. Tractor manufacturers answered by building tractors with four, five or six forward speeds. These additional gears enabled the farmer to better match the tractor’s speed with the task being performed and resulted in a more efficient operation. However, changing gears required engaging the clutch, which in turn often resulted in the tractor stopping, especially when shifting to a slower speed.
Fifty-seven years ago, in 1954, International Harvester introduced the Farmall Super M-TA tractor with its Torque-Amplifier drive. This new type of planetary gear drive enabled the operator to shift from a regular speed to a slower speed by pulling a lever while on-the-go without using the clutch. Shifting to the slower speed increased the pulling power by 48% and decreased the travel speed by 32%. The operator could return to the regular speed by moving the lever in the other direction, again while on-the-go. The Farmall Super M-TA used a five-speed gearbox and the Torque-Amplifier drive to provide 10 forward speeds and two in reverse. It was the first example of what is known today as a partial powershift transmission.
The Farmall Super M-TA was rated as a four-plow tractor with 48-belt horsepower. It was powered with a four-cylinder, 264-cu.-in. International gasoline or diesel engine. The five regular speeds ranged from 2.5 to 16.7 miles per hour and the reduced Torque-Amplifier speeds ranged from 1.7 to 11.3 miles per hour. Torque-Amplifier also enabled an operator to start pulling a heavy wagon in fifth-TA and then shift to the regular fifth gear after getting the load moving. The Super M-TA provided additional flexibility for varying crop conditions with a live PTO and live hydraulics.
Larry Gay is the author of four tractor books published by the American Society of Agricultural and Biological Engineers, including Farm Tractors 1975-1995 and Farm Tractors 1995-2005. These books may be obtained from ASABE at 800-695-2723 or, click publications and then click book catalog.     
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