Copyright by Goodheart-Willcox Co., Inc.
190 Automatic Transmissions and Transaxles
Automatic
transmission
Line
fittings
Radiator
Upper oil
cooler feed
line
Lower oil
cooler return
line
Oil cooler
inside radiator
Line
clamp
Figure 9-4. Steel tubing connects the oil cooler in the radiator to the transmission hydraulic system. Oil is pumped from the torque
converter outlet to the cooler. Cooled oil is directed through the transmission to the components requiring continuous lubrication and
cooling, such as the rear transmission bushings. Excess runs to oil pan, where it is drawn in by the oil pump and distributed else-
where through the system. (General Motors)
the main valve body or to the transmission case. Auxiliary
valve bodies are separated from the main valve body because
of design considerations, such as clearance restrictions.
Valve bodies are used with spacer plates, which are
sometimes referred to as separator plates or transfer plates.
Refer to Figure 9-6. These steel plates seal off passageways
in the valve body and in the transmission case. Spacer
plates are also used between the halves of split valve bod-
ies. Holes are drilled in the spacer plate to connect certain
passageways of mating components.
The spacer plate holes are sized to give a desired flow
rate. In other words, the size of the hole in the spacer plate
dictates how quickly oil can flow through a passageway.
This is to obtain a desired type of shift. Large holes give
quick, hard shifts. Small holes restrict oil flow to lengthen shift
time and cushion shifts. Check balls are often used to block
spacer plate holes, allowing oil to flow in only one direction.
Spacer plates are usually installed with gaskets on both sides.
Oil Transfer Tubes
Many valve bodies are equipped with oil transfer
tubes. Oil transfer tubes are used to connect valve body
pressure chambers when it would be impractical to cast the
needed passages in the valve body or the case. Smaller oil
transfer tubes are usually made of steel tubing, while larger
transfer tubes are made of aluminum. Figure 9-7 shows
how oil tubes are used to connect parts of the valve body
of a typical transmission.
Hydraulic Valves
Hydraulic valves, which were discussed in Chapter 6,
are moving parts of the automatic transmission that act as
pressure and flow controls, directing fluid to various parts
of the transmission. Some hydraulic valves are actuated
manually; others are actuated automatically. For instance,
some hydraulic valves are operated by pressure inputs from
other hydraulic valves, which themselves are operated by
outside factors, such as vehicle speed. Some valves are
located in the valve body, Figure 9-8, while others are posi-
tioned elsewhere in the transmission.
Valves located in the valve body are installed in
drilled holes called valve body bores. The clearance
between the valves and bores is very small, usually less
than 2 thousandths of an inch (0.002″), or 50 thousandths
of a millimeter (0.050 mm). Valves are held in the valve
body bores by snap rings, retaining pins, or retainer plates.
Retainer plates are attached to the end of the valve body
bores by machine screws or small bolts. In addition,
springs made of heat-resistant steel are used in the valve
body to hold valves in position when they are not in
operation.