Chrysler Town & Country/Voyager, Dodge Caravan, Plymouth Voyager. Manual — part 71
LOCKUP TORQUE CONVERTER
The lockup torque converter is standard on all ve-
hicles. The lockup mode is activated only in direct drive
and is controlled by the engine electronics. A lockup
solenoid on the valve body, is powered by the engine
controller to activate torque converter lockup.
HYDRAULIC CONTROL SYSTEM
The hydraulic control circuits show the position of
the various valves with color coded passages to indicate
those under hydraulic pressure for all operations of the
transaxle.
The hydraulic control system makes the transaxle
fully automatic, and has four important functions to
perform. In a general way, the components of any
automatic control system may be grouped into the
following basic groups:
The pressure supply system, the pressure regulating
valves, the flow control valves, the clutches, and band
servos.
Taking each of these basic groups or systems in turn,
the control system may be described as follows:
PRESSURE SUPPLY SYSTEM
The pressure supply system consists of an oil pump
driven by the engine through the torque converter. The
single pump furnishes pressure for all the hydraulic
and lubrication requirements. Oil pump housing
assemblies are available with preselected pump
gears.
PRESSURE REGULATING VALVES
The pressure regulating valve controls line pressure
dependent on throttle opening. The governor valve
transmits regulated pressure to the valve body (in
conjunction with vehicle speed) to control upshift and
downshift.
The throttle valve transmits regulated pressure to
the transaxle (dependent on throttle position) to con-
trol upshift and downshift.
FLOW CONTROL VALVES
The manual valve provides the different transaxle
drive ranges as selected by the vehicle operator.
The 1-2 shift valve automatically shifts the transaxle
from first to second or from second to first, depending
on the vehicle operation.
The 2-3 shift valve automatically shifts the transaxle
from second to third or from third to second depending
on the vehicle operation.
The kickdown valve makes possible a forced down-
shift from third to second, second to first, or third to
first (depending on vehicle speed). This can be done by
depressing the accelerator pedal past the detent ‘‘feel’’
near wide open throttle.
The shuttle valve has two separate functions and
performs each independently of the other. The first is
that of providing fast release of the kickdown band,
and smooth front clutch engagement when the driver
makes a ‘‘lift-foot’’ upshift from second to third. The
second function of the shuttle valve is to regulate the
application of the kickdown servo and band when
making third to second kickdown.
The by-pass valve provides for smooth application of
the kickdown band on 1-2 upshifts.
The lockup solenoid allows for the electronic control
of the lockup clutch inside the torque converter. It also
unlocks the torque converter at closed throttle, during
engine warm-up, and during part-throttle acceleration.
The switch valve directs oil to apply the lockup clutch
in one position and releases the lockup clutch in the
other position.
CLUTCHES, BAND SERVOS, AND ACCUMULA-
TOR
The front and rear clutch pistons, and both servo
pistons are moved hydraulically to engage the clutches
and apply the bands. The pistons are released by
spring tension when hydraulic pressure is released. On
the 2-3 upshift, the kickdown servo piston is released
by spring tension and hydraulic pressure.
The accumulator controls the hydraulic pressure on
the apply side of the kickdown servo during the 1-2
upshift; thereby, cushioning the kickdown band appli-
cation at any throttle position.
GEARSHIFT AND PARKING LOCK CONTROLS
The transaxle is controlled by a ‘‘lever type’’ gearshift
incorporated within the steering column. The control
has six selector lever positions: P (park), R (reverse), N
(neutral), and D (drive), 2 (second), and 1 (first). The
parking lock is applied by moving the selector lever
past a gate to the ‘‘P’’ position. Do not apply the
parking lock until the vehicle has stopped; oth-
erwise, a severe ratchet noise will occur.
TORQUEFLITE DIAGNOSIS AND TESTS
Automatic transaxle malfunctions may be caused by
four general conditions:
(1) Poor engine performance
(2) Improper adjustments
(3) Hydraulic malfunctions
(4) Mechanical malfunctions
Diagnosis of these problems should always begin by
checking the easily accessible variables: fluid level and
condition, gearshift cable adjustment, and throttle
pressure cable adjustment. Then perform a road test to
determine if the problem has been corrected or that
more diagnosis is necessary. If the problem exists after
the preliminary tests and corrections are completed,
hydraulic pressure tests should be performed.
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TRANSAXLE
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TRANSAXLE
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TRANSAXLE
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FLUID LEVEL AND CONDITION
The transmission and differential sump have a
common oil sump with a communicating opening
between the two.
Before removing the dipstick, wipe all dirt off of the
protective disc and the dipstick handle.
The torque converter fills in both the ‘‘P’’ Park and
‘‘N’’ Neutral positions. Place the selector lever in ‘‘P’’
Park to be sure that the fluid level check is accurate.
The engine should be running at idle speed for at
least one minute, with the vehicle on level
ground. This will assure complete oil level stabi-
lization between differential and transmission.
The fluid should be at normal operating temperature
(approximately 82 C. or 180 F.). The fluid level is
correct if it is in the ‘‘HOT’’ region (cross-hatched area)
on the dipstick.
Low fluid level can cause a variety of conditions
because it allows the pump to take in air along with the
fluid. As in any hydraulic system,air bubbles make the
fluid spongy, therefore, pressures will be low and build
up slowly.
Improper filling can also raise the fluid level too
high. When the transaxle has too much fluid, the gears
churn up foam and cause the same conditions which
occur with a low fluid level.
In either case, the air bubbles can cause overheating,
fluid oxidation, and varnishing, which can interfere
with normal valve, clutch, and servo operation. Foam-
ing can also result in fluid escaping from the transaxle
vent (dipstick handle) where it may be mistaken for a
leak.
Along with fluid level, it is important to check the
condition of the fluid. When the fluid smells burned,
and is contaminated with metal or friction material
particles, a complete transaxle overhaul is needed.
DIAGNOSIS GUIDE—ABNORMAL NOISE
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TRANSAXLE
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