Nissan 240SX - Automatic Transmission (Section AT) (2000 year). Manual - part 2

POWER TRANSMISSION

=NMAT0012S04

“N” and “P” Positions

NMAT0012S0401

“N” position
No control members operate. Power from the input shaft is not transmitted to the output shaft since the
clutch does not operate.

“P” position
Similar to the “N” position, no control members operate. The parking pawl interconnected with the select
lever engages with the parking gear to mechanically hold the output shaft so that the power train is locked.

SAT039J

IDX

OVERALL SYSTEM

Shift Mechanism (Cont’d)

AT-17

“1

” Position

=NMAT0012S0406

Forward clutch
Forward one-way clutch
Overrun clutch
Low and reverse brake

As overrun clutch engages, rear internal gear is locked by the operation of low and
reverse brake.
This is different from that of D

and 2

Engine brake

Overrun clutch always engages, therefore engine brake can be obtained when decelerat-
ing.

SAT100J

OVERALL SYSTEM

Shift Mechanism (Cont’d)

AT-18

“D

” and “2

” Positions

=NMAT0012S0402

Forward one-way clutch
Forward clutch
Low one-way clutch

Rear internal gear is locked to rotate counterclockwise because of the functioning of
these three clutches. (Start-up at D

)

Overrun clutch
engagement conditions
(Engine brake)

: Overdrive control switch in “OFF”

Throttle opening less than 3/16

: Throttle opening less than 3/16

At D

and 2

positions, engine brake is not activated due to free turning of low one-way

clutch.

SAT096J

IDX

OVERALL SYSTEM

Shift Mechanism (Cont’d)

AT-19

“D

”, “2

” and “1

” Positions

=NMAT0012S0403

Forward clutch
Forward one-way clutch
Brake band

Rear sun gear drives rear planetary carrier and combined front internal gear. Front inter-
nal gear now rotates around front sun gear accompanying front planetary carrier.
As front planetary carrier transfers the power to rear internal gear through forward clutch
and forward one-way clutch, this rotation of rear internal gear increases the speed of rear
planetary carrier compared with that of the 1st speed.

Overrun clutch
engagement conditions

: Overdrive control switch in “OFF”

Throttle opening less than 3/16

: Throttle opening less than 3/16

: Always engaged

SAT097J

OVERALL SYSTEM

Shift Mechanism (Cont’d)

AT-20

“D

” Position

=NMAT0012S0404

High clutch
Forward clutch
Forward one-way clutch

Input power is transmitted to front planetary carrier through high clutch. And front plan-
etary carrier is connected to rear internal gear by operation of forward clutch and forward
one-way clutch.
This rear internal gear rotation and another input (the rear sun gear) accompany rear
planetary carrier to turn at the same speed.

Overrun clutch
engagement conditions

: Overdrive control switch in “OFF”

Throttle opening less than 3/16

SAT098J

IDX

OVERALL SYSTEM

Shift Mechanism (Cont’d)

AT-21

“D

” (OD) Position

=NMAT0012S0405

High clutch
Brake band
Forward clutch
(Does not affect power transmission)

Input power is transmitted to front carrier through high clutch.
This front planetary carrier turns around the sun gear which is fixed by brake band and
makes front internal gear (output) turn faster.

Engine brake

At D

position, there is no one-way clutch in the power transmission line and engine

brake can be obtained when decelerating.

SAT099J

OVERALL SYSTEM

Shift Mechanism (Cont’d)

AT-22

“R” Position

=NMAT0012S0407

Reverse clutch
Low and reverse brake

Front planetary carrier is stationary because of the operation of low and reverse brake.
Input power is transmitted to front sun gear through reverse clutch, which drives front
internal gear in the opposite direction.

Engine brake

As there is no one-way clutch in the power transmission line, engine brake can be
obtained when decelerating.

SAT101J

IDX

OVERALL SYSTEM

Shift Mechanism (Cont’d)

AT-23

Control System

=NMAT0013

OUTLINE

NMAT0013S01

The automatic transmission senses vehicle operating conditions through various sensors. It always controls
the optimum shift position and reduces shifting and lock-up shocks.

SENSORS

TCM

ACTUATORS

PNP switch
Throttle position sensor
Closed throttle position switch
Wide open throttle position
switch
Engine speed signal
A/T fluid temperature sensor
Revolution sensor
Vehicle speed sensor
Overdrive control switch
A/T mode switch

Shift control
Line pressure control
Lock-up control
Overrun clutch control
Timing control
Fail-safe control
Self-diagnosis
CONSULT-II communication
line
Duet-EA control

Shift solenoid valve A
Shift solenoid valve B
Overrun clutch solenoid valve
Torque converter clutch sole-
noid valve
Line pressure solenoid valve
O/D OFF indicator lamp
POWER indicator lamp

CONTROL SYSTEM

NMAT0013S02

SAT406K

OVERALL SYSTEM

Control System

AT-24

TCM FUNCTION

=NMAT0013S03

The function of the TCM is to:

Receive input signals sent from various switches and sensors.

Determine required line pressure, shifting point, lock-up operation, and engine brake operation.

Send required output signals to the respective solenoids.

INPUT/OUTPUT SIGNAL OF TCM

NMAT0013S04

Sensors and solenoid valves

Function

Input

PNP switch

Detects select lever position and sends a signal to TCM.

Throttle position sensor

Detects throttle valve position and sends a signal to TCM.

Closed throttle position switch

Detects throttle valve’s fully-closed position and sends a signal to TCM.

Wide open throttle position switch

Detects a throttle valve position of greater than 1/2 of full throttle and
sends a signal to TCM.

Engine speed signal

From ECM.

A/T fluid temperature sensor

Detects transmission fluid temperature and sends a signal to TCM.

Revolution sensor

Detects output shaft rpm and sends a signal to TCM.

Vehicle speed sensor

Used as an auxiliary vehicle speed sensor. Sends a signal when revolu-
tion sensor (installed on transmission) malfunctions.

Overdrive control switch
A/T mode switch

Sends a signal, which prohibits a shift to “D

” (overdrive) position, to the

TCM.

Output

Shift solenoid valve A/B

Selects shifting point suited to driving conditions in relation to a signal
sent from TCM.

Line pressure solenoid valve

Regulates (or decreases) line pressure suited to driving conditions in rela-
tion to a signal sent from TCM.

Torque converter clutch solenoid
valve

Regulates (or decreases) lock-up pressure suited to driving conditions in
relation to a signal sent from TCM.

Overrun clutch solenoid valve

Controls an “engine brake” effect suited to driving conditions in relation to
a signal sent from TCM.

O/D OFF or POWER indicator lamp

Shows TCM faults, when A/T control components malfunction.

Control Mechanism

NMAT0180

LINE PRESSURE CONTROL

NMAT0180S01

TCM has the various line pressure control characteristics to meet
the driving conditions.
An ON-OFF duty signal is sent to the line pressure solenoid valve
based on TCM characteristics.
Hydraulic pressure on the clutch and brake is electronically con-
trolled through the line pressure solenoid valve to accommodate
engine torque. This results in smooth shift operation.

IDX

OVERALL SYSTEM

Control System (Cont’d)

AT-25

SAT003J

Normal Control

NMAT0180S0101

The line pressure to throttle opening characteristics is set for suit-
able clutch operation.

SAT004J

Back-up Control (Engine brake)

NMAT0180S0102

If the selector lever is shifted to “2” position while driving in D

(OD)

or D

, great driving force is applied to the clutch inside the trans-

mission. Clutch operating pressure (line pressure) must be
increased to deal with this driving force.

SAT005J

During Shift Change

NMAT0180S0103

The line pressure is temporarily reduced corresponding to a
change in engine torque when shifting gears (that is, when the shift
solenoid valve is switched for clutch operation) to reduce shifting
shock.

At Low Fluid Temperature

NMAT0180S0104

Fluid viscosity and frictional characteristics of the clutch facing
change with fluid temperature. Clutch engaging or band-con-
tacting pressure is compensated for, according to fluid
temperature, to stabilize shifting quality.

SAT006J

The line pressure is reduced below 60°C (140°F) to prevent
shifting shock due to low viscosity of automatic transmission
fluid when temperature is low.

OVERALL SYSTEM

Control Mechanism (Cont’d)

AT-26

SAT007J

Line pressure is increased to a maximum irrespective of the
throttle opening when fluid temperature drops to −10°C (14°F).
This pressure rise is adopted to prevent a delay in clutch and
brake operation due to extreme drop of fluid viscosity at low
temperature.

SHIFT CONTROL

NMAT0180S02

The shift is regulated entirely by electronic control to accommodate
vehicle speed and varying engine operations. This is accomplished
by electrical signals transmitted by the revolution sensor and
throttle position sensor. This results in improved acceleration per-
formance and fuel economy.

SAT008J

Control of Shift Solenoid Valves A and B

NMAT0180S0201

The TCM activates shift solenoid valves A and B according to sig-
nals from the throttle position sensor and revolution sensor to
select the optimum gear position on the basis of the shift schedule
memorized in the TCM.
The shift solenoid valve performs simple ON-OFF operation. When
set to “ON”, the drain circuit closes and pilot pressure is applied to
the shift valve.
[Relation between shift solenoid valves A and B and gear positions]

Shift solenoid valve

Gear position

, 2

, 1

, 2

, 1

(OD)

N-P

ON (Closed)

OFF (Open)

ON (Closed)

OFF (Open)

ON (Closed)

Control of Shift Valves A and B

NMAT0180S0202

SAT047J

IDX

OVERALL SYSTEM

Control Mechanism (Cont’d)

AT-27

Pilot pressure generated by the operation of shift solenoid valves
A and B is applied to the end face of shift valves A and B.
The drawing above shows the operation of shift valve B. When the
shift solenoid valve is “ON”, pilot pressure applied to the end face
of the shift valve overcomes spring force, moving the valve upward.

LOCK-UP CONTROL

NMAT0180S03

The torque converter clutch piston in the torque converter is locked
to eliminate torque converter slip to increase power transmission
efficiency. The solenoid valve is controlled by an ON-OFF duty
signal sent from the TCM. The signal is converted to oil pressure
signal which controls the torque converter clutch piston.

Conditions for Lock-up Operation

NMAT0180S0301

When vehicle is driven in 4th gear position, vehicle speed and
throttle opening are detected. If the detected values fall within the
lock-up zone memorized in the TCM, lock-up is performed.

Overdrive control switch

OFF

Selector lever

“D” position

Gear position

Vehicle speed sensor

More than set value

Throttle position sensor

Less than set opening

Closed throttle position switch

OFF

A/T fluid temperature sensor

More than 40°C (104°F)

SAT010J

Torque Converter Clutch Solenoid Valve Control

NMAT0180S0302

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.

SAT011J

OFF-time INCREASING

Amount of drain DECREASING

Pilot pressure HIGH

Lock-up RELEASING

OVERALL SYSTEM

Control Mechanism (Cont’d)

AT-28

Torque Converter Clutch Control Valve Operation

NMAT0180S0303

SAT048J

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 piston
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 pres-
sure 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)

NMAT0180S04

Forward one-way clutch is used to reduce shifting shocks in down-
shifting 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.

Overrun Clutch Operating Conditions

NMAT0180S0401

Gear position

Throttle opening

“D” position

, D

gear position

Less than 3/16

“2” position

, 2

gear position

“1” position

, 1

gear position

At any position

SAT014J

IDX

OVERALL SYSTEM

Control Mechanism (Cont’d)

AT-29

SAT015J

Overrun Clutch Solenoid Valve Control

NMAT0180S0402

The overrun clutch solenoid valve is operated by an ON-OFF sig-
nal 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.

SAT049J

Overrun Clutch Control Valve Operation

NMAT0180S0403

When the solenoid valve is “ON”, pilot pressure A is applied to the
overrun clutch control valve. This pushes up the overrun clutch
control 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 gener-
ated. At this point, the overrun clutch control valve moves down-
ward by spring force. As a result, overrun clutch operation pressure
is provided 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.

Control Valve

NMAT0181

FUNCTION OF CONTROL VALVE

NMAT0181S01

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
pressure-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 pul-
sations.

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 backpressure 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.

OVERALL SYSTEM

Control Mechanism (Cont’d)

AT-30

Valve name

Function

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 simulta-
neously with application of the brake band in 4th gear. (Interlocking occurs if the
overrun clutch engages during D

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 flowrate 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

“1” reducing valve

Reduces low & reverse brake pressure to dampen engine-brake shock when down-
shifting 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.

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
pressure of the torque converter clutch solenoid valve is generated by a signal
from the control unit.

IDX

OVERALL SYSTEM

Control Valve (Cont’d)

AT-31

CONSULT-II

NMAT0184

After performing “SELF-DIAGNOSTIC PROCEDURE (WITH CON-
SULT-II)” (AT-32), place check marks for results on the “DIAGNOS-
TIC WORKSHEET”, AT-44. Reference pages are provided follow-
ing the items.
NOTICE:
1)

The CONSULT-II electrically displays shift timing and lock-up
timing (that is, operation timing of each solenoid).
Check for time difference between actual shift timing and the
CONSULT-II display. If the difference is noticeable, mechani-
cal parts (except solenoids, sensors, etc.) may be malfunction-
ing. Check mechanical parts using applicable diagnostic pro-
cedures.

Shift schedule (which implies gear position) displayed on
CONSULT-II and that indicated in Service Manual may differ
slightly. This occurs because of the following reasons:

Actual shift schedule has more or less tolerance or allowance,

Shift schedule indicated in Service Manual refers to the point
where shifts start, and

Gear position displayed on CONSULT-II indicates the point
where shifts are completed.

Shift solenoid valve “A” or “B” is displayed on CONSULT-II at
the start of shifting. Gear position is displayed upon completion
of shifting (which is computed by TCM).

Additional CONSULT-II information can be found in the Opera-
tion Manual supplied with the CONSULT-II unit.

SAT014K

SELF-DIAGNOSTIC PROCEDURE (WITH CONSULT-II)

NMAT0184S01

Turn on CONSULT-II and touch “A/T” for TCM self-diagnosis.
If A/T is not displayed, check TCM power supply and ground
circuit. Refer to AT-86. If result is NG, refer to EL-7, “Sche-
matic”.

ON BOARD DIAGNOSTIC SYSTEM DESCRIPTION

CONSULT-II

AT-32

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