Copyright by Goodheart-Willcox Co., Inc.
Chapter 9 Automatic Transmission Control Components 205
have several check balls, which are located next to the
spacer plate and gaskets.
The pressure regulator valve may be in the valve body,
in the back of the oil pump, or in an auxiliary valve body.
It regulates line pressure according to spring pressure and
inputs from other valves.
The manual valve is operated by the driver through the
shift linkage. It allows the driver to select Park, Neutral,
Reverse, or different Drive ranges. When the shift selector
lever is moved, the shift linkage moves the manual valve. As
a result, the valve routes hydraulic fluid to the correct com-
ponents in the transmission.
Shift valves control transmission upshifts and down-
shifts. Hydraulic pressures from the other transmission
valves act on each end of each shift valve.
Throttle valves control the point at which shift valves
move to the upshifted position. They can be operated by
the TV linkage or by the vacuum modulator. Throttle pres-
sure on the shift valves tries to keep them in the down-
shifted position.
Governor valves produce pressure that varies with
vehicle speed. As speed increases, governor pressure
increases. Governors can be mounted on the output shaft
or on the transmission case. Case-mounted governors are
driven by a gear on the output shaft. Governor pressure
opposes throttle pressure to upshift the transmission.
Accumulators cushion shifts by absorbing some of the
fluid being sent to the holding members. The resulting pres-
sure in the accumulator compresses a piston, expanding the
chamber, causing a gradual pressure buildup in the circuit,
and cushioning the shift.
The detent valve forces the transmission into a lower
gear. This is often needed when a vehicle attempts to climb
a hill or accelerate to pass. Detent valves are operated by
linkage or by an electric solenoid.
Check balls are one-way valves. They allow fluid to
flow in one direction only. The steel balls are installed in
chambers next to holes in the valve body spacer plate.
Shift linkage connects the driver to the transmission
through levers and rods or cables. The shift linkage also
operates the neutral start switch, backup lights, and parking
gear mechanism.
Review Questions—Chapter 9
Answer the following questions using the information
provided in this chapter.
1. Cite four functions of an automatic transmission oil
pump.
2. Most of the fluid in an automatic transmission is inside
the _____ _____.
3. All transmission oil pumps are _____ displacement
pumps.
4. Motor-driven pumps are connected to the transmission
hydraulic system by _____.
5. Why must the oil filter be located at the bottom of the
oil pan?
6. Most transmission main oil coolers are installed in the
vehicle _____.
7. Cooled fluid may be routed through the transmission
_____system before returning to the oil pan.
8. Manufacturing tolerances for the _____ _____ must be
exact.
9. Why must the holes in the spacer plate be carefully
sized?
10. Oil transfer tubes connect _____ chambers in the
valve body or case.
11. The _____ controls overall system pressure by exhaust-
ing extra fluid to the oil pan or pump intake.
12. The throttle valve changes position with changes in
engine manifold vacuum. This means that a _____ is
used to operate the throttle valve.
13. The following valve is used to modify pressure
according to vehicle speed _____.
(A) manual valve
(B) throttle valve
(C) governor valve
(D) detent valve
14. Does governor pressure increase or decrease with
road speed? _____ What effect does engine load have
on governor pressure? _____
15. Some automatic transmissions use a _____ valve to
aid downshifting.
16. The hydraulic device used in the apply circuit of a
band or clutch to cushion initial application is the
_____.
(A) synchronizer
(B) accumulator
(C) limiter
(D) regulator
17. The shift linkage transfers motion from the driver to
the _____ valve in the valve body.
18. The _____ _____ switch prevents the engine from
starting when the selector lever is in any position but
Park or Neutral.