Hydrostatic Transmission Other models
2 models in this series
International 544 Hydro: hydrostatic drive with a water-cooled four-cylinder petrol engine delivering 54 hp at the PTO and 42 hp at the drawbar, as a continuously variable tractor
Hydrostatic transmission was, during the 1960s and 1970s, an alternative to the classic gearbox: engine power is transmitted continuously through a hydraulic pump and hydraulic motor instead of a clutch and gear train. The International 544 Hydro is a version of International Harvester's 544 model fitted with this technology.
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The water-cooled four-cylinder petrol engine, type International C-200, ran at 2,400 rpm and, in a tractor test, produced 54 hp at the power take-off and 42 hp at the drawbar. The difference between the two figures corresponds to the usual loss between PTO output and pull at the hitch caused by wheel slip and rolling resistance.
The continuously variable hydrostatic drive made fine control easier during loading work and manoeuvring, since speed and pulling force could be adjusted steplessly without clutching or shifting gears. This advantage came at the cost of somewhat lower mechanical efficiency compared with a classic gearbox.
When buying a hydrostatically driven tractor of this age, the tightness of the hydraulic pump and drive motor is decisive — loss of power or creeping while stationary points to wear on the pistons or valves. The radiator and water pump of the petrol engine, along with the condition of the carburettor gaskets, which often harden and crack on petrol engines of this age, should also be checked.
Sources: SpecCodex-Register: Kennwerte des Modells International 544 Hydro
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