YH4
GRAND
VITARA
1. 4WD switch
2. Transfer
3. Blank
4. Blank
5. ECM or PCM
6. Glove box7. Air pump assembly
8. Actuator
9. Axle lock clutch
10. Free axle hub
11. 4WD indicator lamp
7E-2 DIFFERENTIAL (FRONT)
4WD CONTROL SYSTEM
When the 4WD switch is turned ON by shifting the transfer shift lever, ECM (PCM) (G16 and J20 engine models)
or 4WD controller (H25 engine model) actuates (energizes) the air pump assembly. Then positive pressure is sent
from the air pump assembly to the actuator installed to the differential case and causes the axle lock clutch and
the free axle hub in the differential case to be engaged, resulting in the 4WD mode. Only when running in the 4WD
mode, front axles are joined to differential case, and they become free when 2WD mode is used (or when transfer
shift lever is shifted to N position), thereby reducing the power loss.
YH4
GRAND
VITARA
7E-4 DIFFERENTIAL (FRONT)
Components and Functions
ComponentFunction
4WD switch
When the transfer shift lever is shifted to 4L or 4H position, this switch turns ON
and causes the 4WD control system to turn ON, unless it is shifted to N or 2H
within 1 second.
ECM or PCM
When the 4WD switch turns ON [unless it turns OFF within 1 second], this com-
ponent actuates the pump assembly. If the pressure in the air pump assembly
fails to increase higher than the set level even after the pump motor has run more
than 10 seconds, this component stops the motor to protect it.
Air pump assembly
Pump motor
Release valve
Pressure switchThe air pump assembly consists of a pump motor, release valve and a pressure
switch.
Pump motor:
Produces positive pressure which actuates the actuator.
Release valve:
Closes when transfer shift lever is shifted to 4H or 4L so that the positive pressure
is applied to the actuator, and opens when N or 2H to release the pressure to the
atmosphere.
Pressure switch:
Turns ON and OFF depending on the pressure level in the pump assembly
(whether higher or lower than the set pressure level). ECM or PCM detects the
pressure level through this switch.
Differential case assembly
Free axle hub
Axle lock clutch
ActuatorThe free axle hub, axle lock clutch and actuator are installed in the differential
left case. The positive pressure produced in the air pump assembly is applied
to the actuator which then pushes the axle lock clutch to be engaged with the free
axle hub. In this state, the drive force is transmitted to the front axle, resulting in
the 4WD mode.
When the actuator is free from the positive pressure [when it is under the atmo-
spheric pressure], the axle lock clutch is pushed back by the return spring force
and cannot be engaged with the free axle hub, resulting in the 2WD mode.
ª4WDº indicator lampIt lights up when 4WD control system is in the 4WD mode.
