Page 203 - Hydra-matic 6 Speed RWD Technician's Guide (October 2005)

GLOSSARY OF TECHNICAL TERMS

Input: A starting point for torque, revolutions or energy Residual Fluid Pressure: Excess pressure contained
into another component of the transmission. within an area after the supply pressure has been
terminated.
Internal Gear: The outermost member of a gear set
that has gear teeth in constant mesh with planetary Safety Mode: A condition whereby a component (i.e.
pinion gears of the gear set. engine or transmission) will partially function even if
its electrical system is disabled.
Internal Leak: Loss of fluid pressure in a hydraulic
circuit. Solenoid Valve: An electronic device used to control
transmission shift patterns or regulate fluid pressure.
Land (Valve Land): The larger diameters of a spool
valve that contact the valve bore or bushing. Spool Valve: A cylindrical hydraulic control device
having a variety of land and valley diameters, used to
Line Pressure: The main fluid pressure in a hydraulic control fluid flow.
system created by the pump and pressure regulator
valve. Sprag Clutch: A mechanical clutch (holding device)
consisting of figure eight like elements assembled
Manual Valve: A spool valve that distributes fluid to between inner and outer races.
various hydraulic circuits and is mechanically linked
to the gear selector lever. Throttle Position: The travel of the throttle plate that
is expressed in percentages and measured by the throttle
Orifice: A restricting device (usually a hole in the position (TP) sensor.
spacer plate) for controlling pressure build up into
another circuit. Torque: A measurable twisting force expressed in
terms of Newton-meters (N•m), pounds feet (lbs ft) or
Overdrive: An operating condition in the gear set pounds inches (lbs in).
allowing output speed to be higher than input speed
and output torque to be lower than input torque. Torque Converter: A component of an automatic
transmission, (attached to the engine flywheel) that
Overrunning: The function of a one-way mechanical transfers torque from the engine to the transmission
clutch that allows the clutch to freewheel during certain through a fluid coupling.
operating conditions of the transmission.
Transmission Control Module (TCM): An electronic
Pinion Gear: A small toothed gear that meshes with a device that manages the electrical system of the
larger gear. transmission.

Planet Pinion Gears: Pinion gears (housed in a carrier) Variable Capacity Pump: The device that provides
that are in constant mesh with a circumferential internal fluid for operating the hydraulic circuits in the
gear and centralized sun gear. transmission. The amount of fluid supplied varies
depending on vehicle operating conditions.
Planetary Gear Set: An assembly of gears that consists
of an internal gear, planet pinion gears with a carrier,
and a sun gear.

Pressure: A measurable force that is exerted on an
area and expressed as kilopascals (kPa) or pounds per
square inch (psi).

Pressure Control (PC): An electronic signal that
continuously cycles the ON and OFF time of a device
(such as a solenoid) while varying the amount of ON
time.
Race (Inner or Outer): A highly polished steel surface
that contacts bearings or sprag or roller elements.

Reduction (Gear Reduction): An operating condition
in the gear set allowing output speed to be lower
than input speed and output torque to be higher than
input torque.

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