Hydrostatic transmission (HST) is a type of continuously variable transmission (CVT) system. Its basic task is taking in rotary power (from a rotating location) from the combustion system and transferring that energy onto a load that has predefined traits. HST systems include a variable displacement pump and a fixed displacement motor connected through a series of hose assemblies. HST regulates factors such as speed, power and torque, and steering direction. A hydrostatic transmission uses hydraulic power. There are several disadvantages to such a system.
Vehicles with a hydrostatic transmission have to be driven with extreme care when it comes to acceleration and gears. Light pressure on the pedal can propel the vehicle forward uncontrollably. Even a slight miscalculation can result in the vehicle losing torque and swaying. This makes HST a highly limited choice. It is only used on vehicles such as tractors.