Copyright by Goodheart-Willcox Co., Inc.
192 Automatic Transmissions and Transaxles
Oil transfer
tube
Figure 9-7. The tubes in this illustration connect pressure
passages in the valve body. Using tubes is an alternative to
casting complex extra passages in the valve body or case.
(General Motors)
Figure 9-8. An assembled cast iron valve body used in a nonelectronic transmission. The ridged valve at the top of the valve body
contacts the throttle lever. A pressure switch is installed at the right upper valve body casting.
Springs have other functions as related to hydraulic
valves. In some cases, the springs are used to provide con-
stant resistance that hydraulic pressures work against, such
as in a pressure regulator valve. In other cases, the springs
are used for an initial loading of a valve, to which a varying
hydraulic control pressure is added. Such valves produce a
varying output pressure. In either case, valve springs are
carefully sized to achieve a specified pressure. Specific
springs are used with each valve, and they cannot be inter-
changed. For this reason, care should be taken so springs
are not mixed up when working on the valve body.
There are many types of hydraulic valves used in the
transmission. These include pressure regulator, manual, shift,
throttle, governor, detent, and check valves. A working
knowledge of these valves will help you understand the
internal operation of different transmissions. A brief discus-
sion on each type is presented in the following sections.
(The different valves are explained here on an individual
basis. The operation of these valves as integrated into the
complete hydraulic system is presented in Chapter 12.)