SSANGYONG MY2002
5D1-4 TRANSFER CASE
COMPONENTS OF THE TOD
TRANSFER CASE SYSTEM
Shift Motor
It locates backside transfer case, which drives rotary
helical cam. When mode select switch changes to 4L,
shift fork is on position for 2.48 : 1 by rotation of helical
cam.
Rear Speed Sensor
A hall effect speed sensor which produces a square
wave. 0 to 5 volts direct current signal in response to
a rotating 30-tooth wheel coupled to the rear propeller
shaft inside the transfer case. Each rotation of the rear
propeller shaft will result in 30 speed sensor pulse.
Front Speed Sensor
A hall effect speed sensor which produces a square
wave. 0 to 5 volts direct current signal in response to
a rotating 30-tooth wheel coupled to the front propeller
shaft inside the transfer case. Each rotation of the front
propeller shaft will result in 30 speed sensor pulse.
Electro-Magnetic Clutch
An electromagnetic clutch used to control the amount
of torque applied to the front propeller shaft.
Position Encoder
A set of 4 gray code switches which provide feedback
to the TCCU indicating the position of the shift motor.
Clutch Pedal Position Switch
A switch on vehicles equipped with a manual transmis-
sion which indicates that the clutch pedal is depressed
Park/Neutral Position Switch
A switch on vehicles equipped with an automatic trans-
mission which indicates that the transmission is in neu-
tral.
4H/4L Switch
A switch selects the desired gear ratio.
DEFINITION OF TERMINOLOGY
Shift Inhibit Speed
The vehicle speed limit, which transfer case shifts, is
disallowed. Vehicle speed is indicated by propeller
shaft speed measurement.
Duty Cycle
Duty cycle is the time the electromagnetic clutch is on
divided by the period in which it is being modulated.
Touch-off
A minimum amount of duty cycle applied to the electro
magnetic clutch.
Front Overrun
A condition where the front propeller shaft is turning at
a rate which is faster than the rear propeller shaft.
Rear Overrun
A condition where the rear propeller shaft is turning at
a rate which is faster than the front propeller shaft.
High Range
The highest (numerically lowest = 1 : 1) gear ratio be-
tween the input and outputs of the transfer case.
Low Range
The lowest (numerically highest = 2.48 : 1) gear ratio
between the input and outputs of the transfer case.
OPERATION OF THE TOD
TRANSFER CASE SYSTEM
Initial Operation of TOD Control Unit
When ignition switch is turned to ON, 4WD LOW and
4WD CHECK lamp illuminates for 0.6 second to check
bulb in instrument panel, then perform diagnosis of
system. Refer to “Self-Diagnosis Test” in this section.
Electric Shift System Operation
The electric shift system is responsible for changing
the transfer case gear ratio by controlling the electric
shift motor. The TCCU monitors the 4H/4L switch, park/
neutral position switch, speed sensors, position
encoder, and ignition switch.
A range change is initiated when:
•
The 4H/4L switch is changed from 4H to 4L or from
4L to 4H.
•
The motor position (as indicated by the position
encoder) does not match the 4H/4L switch
immediately after the ignition is turned on.
Shift Criteria
When a range change is initiated a diagnostic test will
be completed on the motor, speed sensors, and
position encoder. If the diagnostic test fails, the shift
will not be attempted. If all components are operating
properly, the TCCU will attempt a range change after
the following shift criteria are met:
•
The transmission is in neutral for 2 seconds after
the shift is requested.
•
Both propeller shaft speeds are below 87 rpm (2580
pulses/minute). If the transmission is taken out of
neutral before 2 seconds has passed, or either
propeller shaft speed increases above the limit, the
shift will be suspended and the 4L indicator will
continue to blink until the criteria are met again or
the 4H/4L switch is returned to the original position.
Range Change
When the shift criteria are met, the motor is rotated in
the appropriate direction (as determined by the selector
switch) until one of the following occurs: