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Tractor Trendsetters: International 656 Hydro

Mar 07, 2013

Tractor Trendsetters: International 656 Hydro

Written by Larry Gay

The earliest tractors were built with one forward speed and one in reverse. Soon the tractor manufacturers upgraded their transmissions to provide two or three forward speeds to provide a more optimum speed for different field operations. Rubber tires in the mid-1930s enabled the tractor to travel faster on the road and a "road speed" was added. Over the years the number of forward speeds continued to increase to 10 or 12. International Harvester introduced a hydrostatic drive for its 656 tractor in the summer of 1967. The ability of this tractor to provide an infinite number of forward speeds between 0 and 20 mph made the 656 Hydro a tractor trendsetter.

The hydrostatic transmission consisted of an engine-driven piston-type pump which delivered pressurized oil to a piston-type motor. The motor was connected to a 2-speed transmission which provided speeds of 0 to 8 mph in the low range and 0 to 20 mph in the high range. The Speed Ratio lever, mounted on the left side of the dash, controlled the volume of oil being pumped and thus the speed of the tractor. Moving the lever forward from the neutral position increased the forward speed and moving it rearward from the neutral position increased the speed in reverse, up to 4 mph in low range and up to 9 mph in high range.

The infinite number of speeds provided the exact desired speed for planting and applying chemicals. The ability to change speeds easily and quickly worked very well to match the speed with varying crop conditions when the tractor was used with PTO-driven harvesting machines. The hydrostatic transmission was convenient for loader work as the tractor could be shifted from forward to reverse without using a clutch. The Foot-N-Inch pedal was not a clutch pedal, but it acted as one, allowing easier hookups with implements and stopping the tractor for emergencies.

The 656 was built as a Farmall (row crop) version and as an International (utility) version. Both versions offered a choice of a gear-drive transmission or the hydrostatic transmission. Those with the hydrostatic transmission had "Hydro" written on the sides of the hood. The 656 was powered by 6-cylinder International engines, with a displacement of 263 cubic inches for the gasoline engine and 282 cubic inches for the diesel. Both engines of the Hydro version produced about 66 PTO horsepower at the Nebraska tests.

By 1970 International Harvester had four models of farm tractors with a hydrostatic transmission—the 544 Hydro, the 656 Hydro, the 826 Hydro, and the 1026 Hydro. Today hydrostatic transmissions are used in lawn tractors, compact tractors, and the New Holland TV 145 bi-directional tractor.

Larry Gay is the author of four tractor books and the "Machinery Milestones" articles in Heritage Iron magazine. To learn more about this magazine which focuses on the 1960-1985 era, go to or call 1-855-old iron.

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