Opel Frontera UE. Manual - part 690

4B–2

DRIVELINE CONTROL SYSTEM

Shift On The Fly System

Outline of Shift on The Fly System

The shift on the fly system switches between 2 wheel 
drive (2WD) and 4 wheel drive (4WD)  electrically by 
driver's pressing the 4WD switch (push button type) on 
instrument panel.
This system controls below operations. (Shifting 
between “4H" and “4L" must be performed by transfer 
control lever on the floor.)

1. Shifting the transfer front output gear (Connecting 

to, and disconnecting from, front propeller shaft by 
motor actuator).

2. Retrial of shifting the transfer front output gear.

3. Connecting front wheels to, and disconnecting them 

from, the front axles by vacuum actuator.

4. Indicator on instrument panel.

5. 4WD out signal to other Electronic Hydraulic Control 

Unit.

System Diagrams

412RX009

DRIVELINE CONTROL SYSTEM

4B–3

Normal Operation

The motor actuator mounted on transfer rear case is 
driven by signal from 4WD switch on instrument panel.  
After complete the connecting transfer front output gear 
to, or disconnecting it from, front propeller shaft, 

condition of the transfer position switch changes. The 
vacuum solenoid valve (VSV) is driven by the signal 
from transfer position switch and the vacuum actuator 
connects front wheels to, or disconnect them from, front 
axles.

Time Chart of Shifting Under Normal Condition

F04RW002

4B–4

DRIVELINE CONTROL SYSTEM

Retrial

The motor actuator starts transfer gear shifting after 
signal from 4WD switch on instrument panel has been 
received.  But the shifting may be impossible in cold 
weather or under high speed condition.  When 2 
seconds have passed since transfer gear shifting 
started and the transfer position switch dose not turn on 
(the gear engagement is not completed), the motor 
reverses its rotation for 1.2 seconds and tries again to 
shift transfer gear.  This procedure is repeated 3 times 

in maximum.  While this procedure, 4WD indicator lamp 
blinks by 2 Hz.
If the transfer position switch does not turn on after 
aforementioned procedure has been repeated 3 times, 
the gear shifting is stopped and 4WD indicator lamp's 
blinking changes from 2Hz to 4Hz to notify driver that 
the gear shifting is stopped.  This blinking of indicator 
lamp continues until 4WD switch is returned from 4WD 
to 2WD.

Time Chart of Shifting Under Severe Condition (retrial)

F04RX004

DRIVELINE CONTROL SYSTEM

4B–5

Warning at “4L" position :In view of the shifting 
mechanism of transfer, the gear shifting from 4WD to 
2WD at “4L" condition is impossible.  Therefore, the 
transfer position switch can not be turned off by 4WD 

switch when vehicle is in “4L" condition.  In the case this 
condition continues for 2 seconds, the shifting to 2WD is 
stopped and the indicator lamp's blinking changes from 
2Hz to 4Hz to notify driver of wrong operation.

Time Chart of Shifting from 4WD to 2WD at “4L" Condition

F04RX005

4WD out signal to other Electronic Hydraulic 
Control Unit : ECU of shift on the fly sends 4WD out 
signal to other Electronic Hydraulic Control Unit as 
below.

4WD out signal

(Period)

Vehicle Condition

Transfer position switch

Front axle switch

120 ms

2WD

2WD (Open)

2WD (Open)

240 ms

4WD

4WD (Close)

4WD (Close)