Module 2- Apply and Hold Devices (Page 6 of 6)
Dual Function of Transmission Components
Transmission planetary gear components often perform two or more functions. Sometimes they must be held stationary. Other times the same component must be connected to the engine.
For example: the ring / internal gear of the planetary gear set is held stationary in Drive 1 - maximum reduction. See diagram below.
But when the transmission shifts to the next gear, Drive 2 - moderate reduction, the internal / ring gear is attatched to the engine (input). See diagram below.
How is this possible?
The internal gear is attached to a drum housing. See diagram below. In Drive 1 - the valve body actuates the servo to apply the band and wrap it around the drum. The drum is held stationary. Since the drum is attatched to the internal gear, the internal gear is also held stationary.
When the valve body decides the transmission should shift into Drive 2, it does two things at the same time. First, it releases the brake band. The ring / internal gear is no longer held.
Second, a clutch pack is simultaneously applied which connects the ring / internal gear to the input shaft. The internal / ring gear is now being driven by the engine.
We have just shifted from Drive 1 to Drive 2.
Module 2 (Page 6 of 6)