Nissan Frontier D22. Manual — part 53
OVERALL SYSTEM
AT-181
[RE4R01A]
D
E
F
G
H
I
J
K
L
M
A
B
AT
Torque Converter Clutch Solenoid Valve Control
The torque converter clutch solenoid valve is controlled by the TCM.
The plunger closes the drain circuit during the OFF period, and
opens the circuit during the ON period. If the percentage of OFF-time
increases in one cycle, the pilot pressure drain time is reduced and
pilot pressure remains high.
The torque converter clutch piston is designed to slip to adjust the
ratio of ON-OFF, thereby reducing lock-up shock.
OFF-time INCREASING
↓
Amount of drain DECREASING
↓
Pilot pressure HIGH
↓
Lock-up RELEASING
Torque Converter Clutch Control Valve Operation
Lock-up Released
The OFF-duration of the torque converter clutch solenoid valve is long, and pilot pressure is high. The pilot
pressure pushes the end face of the torque converter clutch control valve in combination with spring force to
move the valve to the left. As a result, converter pressure is applied to chamber A (torque converter clutch pis-
ton release side). Accordingly, the torque converter clutch piston remains unlocked.
Lock-up Applied
When the OFF-duration of the torque converter clutch solenoid valve is short, pilot pressure drains and
becomes low. Accordingly, the control valve moves to the right by the pilot pressure of the other circuit and
converter pressure. As a result, converter pressure is applied to chamber B, keeping the torque converter
clutch piston applied.
Also smooth lock-up is provided by transient application and release of the lock-up.
OVERRUN CLUTCH CONTROL (ENGINE BRAKE CONTROL)
Forward one-way clutch is used to reduce shifting shocks in downshifting operations. This clutch transmits
engine torque to the wheels. However, drive force from the wheels is not transmitted to the engine because
the one-way clutch rotates idle. This means the engine brake is not effective.
The overrun clutch operates when the engine brake is needed.
SAT010J
SAT011J
SAT048J
AT-182
[RE4R01A]
OVERALL SYSTEM
Overrun Clutch Operating Conditions
Overrun Clutch Solenoid Valve Control
The overrun clutch solenoid valve is operated by an ON-OFF signal
transmitted by the TCM to provide overrun clutch control (engine
brake control).
When this solenoid valve is ON, the pilot pressure drain port closes.
When it is OFF, the drain port opens.
During the solenoid valve ON pilot pressure is applied to the end
face of the overrun clutch control valve.
Overrun Clutch Control Valve Operation
When the solenoid valve is ON, pilot pressure A is applied to the
overrun clutch control valve. This pushes up the overrun clutch con-
trol valve. The line pressure is then shut off so that the clutch does
not engage.
When the solenoid valve is OFF, pilot pressure A is not generated. At
this point, the overrun clutch control valve moves downward by
spring force. As a result, overrun clutch operation pressure is pro-
vided by the overrun clutch reducing valve. This causes the overrun
clutch to engage.
In the 1 position, the overrun clutch control valve remains pushed
down so that the overrun clutch is engaged at all times.
SAT014J
Gear position
Throttle opening
D position
D
1
, D
2
, D
3
gear position
Less than 3/16
2 position
2
1
, 2
2
gear position
1 position
1
1
, 1
2
gear position
At any position
SAT015J
SAT049J
OVERALL SYSTEM
AT-183
[RE4R01A]
D
E
F
G
H
I
J
K
L
M
A
B
AT
Control Valve
ECS007LM
FUNCTION OF CONTROL VALVE
Valve name
Function
●
Pressure regulator valve
●
Pressure regulator plug
●
Pressure regulator sleeve plug
Regulate oil discharged from the oil pump to provide optimum line pressure for all driving
conditions.
Pressure modifier valve
Used as a signal supplementary valve to the pressure regulator valve. Regulates pres-
sure-modifier pressure (signal pressure) which controls optimum line pressure for all
driving conditions.
Modifier accumulator piston
Smooths hydraulic pressure regulated by the pressure modifier valve to prevent pulsa-
tions.
Pilot valve
Regulates line pressure to maintain a constant pilot pressure level which controls lock-up
mechanism, overrun clutch, 3-2 timing required for shifting.
Accumulator control valve
Accumulator control sleeve
Regulate accumulator back-pressure to pressure suited to driving conditions.
Manual valve
Directs line pressure to oil circuits corresponding to select positions.
Hydraulic pressure drains when the shift lever is in Neutral.
Shift valve A
Simultaneously switches three oil circuits using output pressure of shift solenoid valve A
to meet driving conditions (vehicle speed, throttle opening, etc.).
Provides automatic downshifting and up-shifting (1st
→ 2nd → 3rd → 4th gears/4th →
3rd
→ 2nd → 1st gears) in combination with shift valve B.
Shift valve B
Simultaneously switches three oil circuits using output pressure of shift solenoid valve B
in relation to driving conditions (vehicle speed, throttle opening, etc.).
Provides automatic downshifting and up-shifting (1st
→ 2nd → 3rd → 4th gears/4th →
3rd
→ 2nd → 1st gears) in combination with shift valve A.
Shuttle shift valve S
Switches hydraulic circuits to provide 3-2 timing control and overrun clutch control in
relation to the throttle opening.
Inactivates the overrun clutch to prevent interlocking in 4th gear when the throttle is wide
open.
Overrun clutch control valve
Switches hydraulic circuits to prevent engagement of the overrun clutch simultaneously
with application of the brake band in 4th gear. (Interlocking occurs if the overrun clutch
engages during D
4
gear operation.)
4-2 relay valve
Memorizes that the transmission is in 4th gear. Prevents the transmission from down-
shifting from 4th gear to 3rd and then to 2nd in combination with 4-2 sequence valve and
shift valves A and B when downshifting from 4th to 2nd gear.
4-2 sequence valve
Prevents band servo pressure from draining before high clutch operating pressure and
band servo releasing pressure drain (from the same circuit) during downshifting from 4th
to 2nd gear.
Servo charger valve
An accumulator and a one-way orifice are used in the 2nd gear band servo oil circuit to
dampen shifting shock when shifting from 1st to 2nd gear.
To maintain adequate flow rate when downshifting from 4th or 3rd gear to 2nd gear, the
servo charger valve directs 2nd gear band servo hydraulic pressure to the circuit without
going through the one-way orifice when downshifting from 3rd or a higher gear.
3-2 timing valve
Prevents a late operation of the brake band when shifting selector lever from D to 1 or 2
position while driving in D
3
.
1 reducing valve
Reduces low & reverse brake pressure to dampen engine-brake shock when downshift-
ing from the 1 position 2nd gear to 1st gear.
Overrun clutch reducing valve
Reduces oil pressure directed to the overrun clutch and prevents engine-brake shock.
In 1 and 2 positions, line pressure acts on the overrun clutch reducing valve to increase
the pressure-regulating point, with resultant engine brake capability.
Torque converter relief valve
Prevents an excessive rise in torque converter pressure.
AT-184
[RE4R01A]
OVERALL SYSTEM
Torque converter clutch control valve,
torque converter clutch control plug and
torque converter clutch control sleeve
Activate or inactivate the lock-up function.
Also provide smooth lock-up through transient application and release of the lock-up
system.
Shuttle shift valve D
Switches hydraulic circuits so that output pressure of the torque converter clutch sole-
noid valve acts on the lock-up valve in the D position of 2nd, 3rd and 4th gears. (In the D
position 1st gear, lock-up is inhibited.)
●
Lock-up control is not affected in D position 2nd, 3rd or 4th gears, unless output pres-
sure of the torque converter clutch solenoid valve is generated by a signal from the
control unit.
Valve name
Function
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