Service Manual

128 P Series
Hydrostatic Transmission: The combination of a hydraulic pump and motor in one housing to
form a device for the control and transfer of power.
Inlet Line: A supply line to the pump.
Integrated Hydrostatic Transaxle (IHT): The combination of a hydrostatic transmission and
gear case in one housing to form a complete transaxle.
Manifold: A conductor which provides multiple connection ports.
Neutral: Typically described as a condition in which fluid flow and system pressure are below
that which is required to turn the output shaft of the motor.
Pressure Decay: A falling pressure.
Priming: The filling of the charge circuit and closed loop of the fluid power system during
start-up, frequently achieved by pressurizing the fluid in the inlet line.
Purging: The act of replacing air with fluid in a fluid power system.
Rated Flow: The maximum flow that the pump is capable of supplying.
Scoring: Scratches in the direction of motion of mechanical parts caused by abrasive contami-
nants.
Shock Valve: A relief valve in the closed loop of the hydrostatic circuit that provides makeup oil,
as well as protecting the circuit from high pressure shocks or spikes.
Swashplate: A mechanical device used to control the displacement of the pump pistons in a fluid
power system.
System Charge Check Valve: A valve controlling the replenishing flow of fluid from a charge
circuit to the closed loop in a fluid power system.
System Pressure: The pressure which overcomes the total resistance in a system, including all
efficiency losses.
Valve: A device which controls fluid flow direction, pressure, or flow rate.
Variable Displacement Pump: A pump in which the displacement per revolution can be varied.
Volumetric Displacement: The fluid volume for one revolution.