Hydraulic transformer
*Transmits torque from the engine to the gearbox.
* Consists of pump, turbine and stator.
* Multiplies torque at low speeds and acts like a clutch.
Planetary gear
* Consists of a central shaft (sun gear), planetary gears and carrier (outer gear).
* Used to change the gear ratio by turning different gear combinations on or off.
Hydraulic control unit
* Controls the flow of fluid through the transmission.
* Consists of valves and solenoids.
* Directs fluid to the appropriate passages to engage and disengage gears.
4th stage body
*Contains planetary gears for four gear ratios (first, second, third and fourth).
*Also contains friction discs and steel plates which are used to engage and disengage gears.
Operating procedure
First gear:
* The selector valve directs fluid into a passage that engages the first gear friction discs.
* The first gear planetary gear is locked to provide the smallest gear ratio.
Second gear:
* The selector valve directs fluid into a passage that engages the second gear friction discs.
* The first gear planetary gear is unlocked and the second gear planetary gear is locked, providing a higher gear ratio.
Third gear:
* The selector valve directs fluid into a passage that engages the third gear friction discs.
* The first and second gear planetary gears are unlocked, and the third gear planetary gear is locked, providing an even higher gear ratio.
Fourth gear:
* The selector valve directs fluid into a passage that engages the fourth gear friction discs.
* The first, second and third gear planetary gears are unlocked and the fourth gear planetary gear is locked, providing the highest gear ratio (direct drive).