Isuzu KB P190. Manual - part 1107

7A2-144   TRANSMISSION CONTROL SYSTEM (JR405E)

The JR405E automatic transmission is electrically
controlled by a transmission control module (TCM).
There are four forward speeds and one reverse speed.
This JR405E automatic transmission employs a clutch
pressure direct control system (Direct Electronic Shift
Control: DESC) using duty cycle type solenoid valves,
which ensure high shift quality. This transmission also
has a learning function and constantly checks the time
of each clutch and brake required for the shift in order
to match this time with the target value for the optimum
shift. The TCM will automatically select the most
appropriate shift points and lock-up points depending
on the accelerator pedal opening, the vehicle speed
and the vehicle load. If any trouble arises in the speed
sensor, solenoid valve, etc., the fail-safe control
function is activated to keep the running performance.
The JR405E automatic transmission consists of the
torque converter, oil pump, input shaft, out put shaft,
planetary gears and valve body. The gear train consists
of two planetary gear sets and three multiple plate
clutches in combination with two multiple plate brakes
and a one-way clutch.

Transmission Component Description

Torque Converter

Legend

1. Pump impeller
2. Turbine runner
3. Stator 
4. Converter front cover
5. One-way clutch
6. Torque converter clutch (TCC) piston
7. Torsion damper

The torque converter is a device for transmitting the
engine torque to the transmission. It transmits power by
means of oil when the lock up clutch is disengaged,
and by means of a lock up clutch when it is engaged. 

The torque converter is of the symmetrical, three-
element, single-stage, two-phase type. As shown in the
picture, the symmetrical three-elements refer to three
elements (components) consisting of impeller (1),
turbine (2) and stator (3) that are arranged
symmetrically. Single-stage means that there is only
one turbine as an output element; two-phase means
that the pump impeller acts as a torque converter when
the turbine speed is comparatively low, and as a fluid
coupling when the speed is high. Lock up refers to a
fixed state of the lock up clutch (=torque converter
clutch (TCC) inside the torque converter and thus
connects the engine directly to the transmission.

Oil Pump

Legend

1. Torque converter
2. Oil pump

TRANSMISSION CONTROL SYSTEM (JR405E)   7A2-145

Legend

1. Oil pump cover
2. Inner rotor 
3. Outer rotor
4. Oil pump housing

The oil pump generating oil pressure is a small sized
trochoid gear type oil pump. It feeds oil to the torque
converter, lubricates the power train mechanism, and
feeds the oil pressure to the oil pressure control unit
under pressure. The oil pump is located behind the
torque converter. Since the inner rotor in the oil pump is
fitted with the drive sleeve of the torque converter, it
works using power from the engine. 

Legend

1. Pressure regulator valve
2. Outlet 
3. Inlet

When the inner rotor in the oil pump rotates,
transmission fluid is sucked in from the oil pan, passed
between the inner rotor, outer rotor and crescent, and
then discharged. This discharged pressure is sent to
the pressure regulator valve in the valve body, and
adjusted as required for operating the transmission.
The flow rate under pressure increases or decreases in
proportion to the number of rotations.

Input Shaft 

The input shaft has some oil holes, through which
lubricating transmission fluid is supplied to the torque
converter, the bearings, etc. The input shaft is fitted to
the turbine runner in the torque converter, the reverse &
high clutch drum and the rear sun gear by means of the
spline. Therefore, the engine driving force received by
the torque converter is transmitted to the reverse &
high clutch drum and rear sun gear.

Output Shaft

The output shaft has some oil holes, through which the
lubricating transmission fluid is supplied to the
bearings, the planetary gear unit, etc. The output shaft
transmits the engine driving force from the planetary
gear to the propeller shaft. The front internal gear is
fitted with the rear carrier assembly by spline. The
parking gear is also fitted by spline. By fixing this gear
mechanically, the output shaft is fixed as required when
parking the vehicle.

7A2-146   TRANSMISSION CONTROL SYSTEM (JR405E)

Low Clutch, High Clutch and Reverse Clutch 

Legend

1. Clutch
2. Clutch drum
3. Clutch piston
4. Clutch fluid pressure 
5. Clutch chamber
6. Oil seal
7. Lunrication circuit
8. Centrifugal balance chamber
9. Centrifugal cancel cover 

10. Return spring

11. Piston check ball

The multi-plate clutch is composed of drive plates and
driven plates. By applying the oil pressure onto the end
surface of the plates, the clutch is engaged. The oil
pressure is adjusted with the spool valves according to
the signal from the TCM. All clutches use dish plates to
prevent uncontrolled operation of the clutches when
engaged, causing a shock. 

For the low clutch and high clutch (A), a centrifugal
balance chamber full of transmission fluid is provided to
offset the excessive oil pressure. This prevents clutch
drag caused by oil pressure generated by residual
transmission fluid due to the centrifugal force while the
clutch is racing (under no oil pressure).
For the reverse clutch (B), a piston check ball is used to
release the oil pressure. This prevents clutch drag
caused by oil pressure generated by residual
transmission fluid due to the centrifugal force while the
clutch is racing (under no oil pressure). 
The solenoid valve in the valve body is driven based on
the shift signal from the TCM, it moves the shift valve,
thereby engaging the drive plate and driven plate
through the piston of each clutch. As a result, elements
of the planetary gear unit are combined. When the oil
pressure is removed, the piston returns to the original
position via the force of the return spring.

2-4 Brake and Low & Reverse Brake 

The multi-plate brake is composed of drive plates and
driven plates. By applying the oil pressure onto the end
surface of the plates, the brake is engaged. The oil
pressure is adjusted with the spool valve according to
the signal from the TCM. All brakes use dish plates to
prevent uncontrolled operation of the clutches when
engaged, causing a shock.
The solenoid valve in the valve body is driven based on
the shift signal from the TCM, it moves the shift valve,
thereby engaging the drive plate and driven plate
through the piston of each brake. As a result, rotation of
each element of the planetary gear unit is fixed. When
the oil pressure is removed, the piston returns to the
original position via the force of the return spring.

TRANSMISSION CONTROL SYSTEM (JR405E)   7A2-147

Low One-way Clutch

Legend

1. Sprag
2. Rotating direction

The low one-way clutch employs the sprag, which locks
the counterclockwise rotation of the front planetary
carrier and the rear internal gear. The one-way clutch
outer race is fitted with the low clutch drum, and the
inner race is fitted with the transmission case. The
outer race rotates freely clockwise, but, when it
attempts to rotate counterclockwise, the sprag locks
the outer race. When the vehicle is traveling in 1st gear
in the D, 3 or 2 position, the low one-way clutch locks
the rear internal gear via the low clutch. It is left free in
the 2nd, 3rd or 4th gear.

Parking Function

Legend

1. Parking pawl
2. Parking pawl shaft
3. Pawl return spring
4. Parking actuator support
5. Manual plate
6. Parking cam
7. Parking gear
8. Parking rod

By setting the selector lever to the P range, the parking
pawl is engaged with the parking gear and fixes the
output shaft. By moving the selector lever, the manual
shaft on the right side of the transmission is moved.
The manual plate and parking rod in the transmission is
interlocked with the manual shaft. When the manual
shaft moves, the parking rod end pushes up the parking
pawl. The parking pawl is engaged with the parking
gear when pushed up, and fixes the output shaft. When
the parking is disengaged, it returns to the original
position via the force of the return spring.