Hydraulic System Operation
The hydraulic system shown in figure 7-19 has the
following five basic functions.
1. The planetary holding devices are all actuated
by hydraulic pressure from hydraulic slave
systems (fig. 7-20).
2. It keeps the torque converter charged with fluid
at all times.
The shifting pattern is controlled by the
hydraulic system by switching hydraulic line
Figure 7-20.Lockup band actuated by hydraulic pressure.
pressure to programmed shifting devices
according to vehicle speed and load.
It circulates the oil through a remote oil cooler
5. The hydraulic system provides a constant supply
to remove excess heat that is generated in the
of lubricating oil to all critical wearing surfaces
transmission and torque converter.
of the transmission.
Figure 7-19.Typical hydraulic schematic of a three-speed automatic transmission.