Isuzu Amigo / Axiom / Trooper / Rodeo / VehiCross. Manual - part 96

DRIVE LINE CONTROL SYSTEM (TOD)

4B2–2

General Description

412R200008

TOD (Torque on Demand) system is traction state control
system to vehicle.

Transfer Position and Drive Mode

Three drive modes can be selected through operation of
TOD switch and transfer lever.

Transfer Position

TOD SWITCH

Mode

Drive mode

HIGH

2H

RWD

Rear wheel drive

TOD

4WD

(HIGH)

Electronically controlled torque split
four wheel drive

LOW

4L

4WD

(LOW)

Low-speed mechanical lock-up four
wheel drive

The electronic control unit (ECU) judges the signals from
the TOD switch and controls the transfer drive mode and
shift-on-the-fly system status.

4B2–3

DRIVE LINE CONTROL SYSTEM (TOD)

TOD Control

The TOD position usually drives the rear wheels, and
transmits the torque to the front wheels with the help of
electronically controlled torque split mechanism
according to running conditions encountered. The driving
force is directly transmitted to the rear wheels. This force
is split by the transfer and delivered to the front wheels.
The magnitude of the torque transmitted to the front
wheels is controlled by changing the pressing force of the
multi plate disk clutch built in the transfer unit. The
pressing force of the clutch is controlled by changing the
duty ratio to the electromagnetic coil mounted to the rear
of the clutch. When the clutch is completely disengaged,
the rear wheels are driven. When the clutch is completely
engaged, a rigid four wheel drive mode is obtained. The
torque split status is controlled continuously between the
rear wheel and four wheel drive modes. This system
includes front and rear speed sensors, and receives
throttle position sensor and engine speed information
from the PCM, ABS control unit signal, brake switch
signal, and shift motor position information.
The control unit receives signals sent from these sensors
and changes the pressing force of the multi-plate disk
clutch to determine the torque distribution on the front and
rear wheels. Therefore, when the slip of the rear wheels is
increased against the current torque level in the normal
rear wheel drive mode, the control unit detects the slip
condition, determines the optimum torque based on the
feedback control logic, and increases the torque to the
front wheels.
The control unit uses the signal from the throttle position
sensor to predict the future vehicle condition and the
intention of the driver with respect to acceleration and
deceleration, and determines the initial torque distribution
using these data and the information from the speed
sensors.
In case of small circle turning in the parking lot, for
example, the control unit minimizes the clutch pressing
force to restrict a braking phenomenon. When the ABS
becomes active, the control unit optimizes the clutch
pressing force to ensure stable braking.

TOD Indicator Control

The TOD indicator on the instrument panel informs the
driver of the current working status of the transfer unit.
The information is the drive mode (2H, TOD, 4L,
transition). The indicator can display occasional errors
and corresponding error codes.

Abbreviations

ABS

Anti-lock Brake System

ADC

Axle Disconnect
(Shift on the fly system)

VB

Battery Voltage

VIGN

Ignition Voltage

DRIVE LINE CONTROL SYSTEM (TOD)

4B2–4

System Components

Parts Location

A04R200004

Legend

(1) Mechanical Lock Sleeve
(2) Drive Chain
(3) Clutch Pack
(4) Electromagnetic Clutch Solenoid
(5) Output Shaft
(6) Rear Output Coupling
(7) Rear Speed Sensor
(8) Drive Sprocket
(9) Spring

(10) Return Spring

(11) Lockup Shift Fork

(12) Front Speed Sensor
(13) High-Low Shift Motor
(14) Driven Sprocket

(15) Shift Shaft
(16) Front Output Coupling
(17) Front Output Shaft
(18) Shift Cam
(19) Torsional Spring
(20) High-Low Shift Fork
(21) Shift Rod
(22) Input Shaft
(23) Reduction Hub
(24) High-Low Planetary Gear
(25) High Position
(26) Low Position
(27) Oil Pump
(28) Free Position
(29) Lock Position

4B2–5

DRIVE LINE CONTROL SYSTEM (TOD)

Front and Rear Speed Sensors

The sensors are built in the transfer case, and detect the
rotation of rotors directly coupled to the propeller shafts.
Thirty rectangular pulses are output per one rotation of
the propeller shaft.

261RW045

Electromagnetic Coil

Receives the duty signals from the TOD control unit and
controls the pressing force of the clutch pressure cam.

261RW044

Multi Plate Disk Clutch Pack

Transmits the torque determined by the clutch pressing
force to the front propeller shaft via the front drive chain.

262RW029

Mechanical Lock Sleeve

Couples the front and rear propeller shaft mechanically
when the transfer shaft is in the 4L position.

262RW028