308-07A Four-Wheel Drive Systems: Description And Operation (page 27 of 30)

Mud/Ruts  
Sand  
Rock crawl.  

The Terrain Response™ system uses a combination of vehicle subsystems to achieve the required vehicle characteristics 
for the terrain selected. The following subsystems form the Terrain Response™ system:  
 

Engine management system  
Automatic transmission (if fitted)  
Transfer box  
Rear locking differential (if fitted)  
Brake system  
Air suspension.  

Each subsystem control module provides a feedback for the selected program so that the Terrain Response™ control 
module can check that all systems are controlling the system correctly. For additional information, refer to   

Ride and 

Handling Optimization

 (204-06 Ride and Handling Optimization) 

HIGH RANGE OPERATION 

In high range, the torque input from the transmission is passed to the transfer box input shaft. The position of the 
synchroniser sleeve couples the shaft directly to the differential housing. The differential splits the torque between the two 
side gears. One side gear is connected by splines and passes the torque to the rear output flange. The second side gear 
is connected to the chain drive sprocket and passes the torque, via the chain, to the front output flange. 
 

LOW RANGE OPERATION 

In low range, the torque input from the transmission is passed to the transfer box input shaft. The synchroniser sleeve is 
moved and connects the planetary carrier to the differential housing. The torque from the transmission is now directed 
through the sun gear of the epicyclic gearset and, via the pinion gears and pinion gear shafts, into the planetary carrier. 
The annulus gear of the epicyclic gearset is secured inside the casing and generates the low range ratio of 2.93:1. The 
torque is then passed, via the synchroniser sleeve, to the differential housing where it is split between the two side gears. 
One side gear is connected by splines and passes the torque to the rear output flange. The second side gear is 
connected to the chain drive sprocket and passes the torque, via the chain, to the front output flange. 
 

HIGH/LOW RANGE GEARS WITH SHIFT-ON-THE-MOVE 

The driver is able to change between high and low range gears while the vehicle is moving, or if the vehicle is stationary.
 
Pushing the range change lever makes a range change requests. This lever is located on the centre console behind and 
to one side of the main transmission lever. 
 
The driver requests a high to low range change by pushing the range change lever towards the rear of the vehicle and, 
conversely, a low to high request by pushing the lever towards the front of the vehicle. The range change lever is centre 
sprung and therefore does not latch in the forward or rear positions. 
 
The driver is informed of the range status via a green lamp (mountain symbol) in the instrument cluster and LED's next to 
the range change lever. The lamp will not be illuminated in high range, illuminated in low range and flashing during a 
range change. There are two LED's on the range change lever one for high and one for low. During a range change the 
new range LED will flash. 
 
The vehicle will remain in the selected range unless the driver requests a change, i.e. it will not automatically revert to 
high range following a key off/key on sequence.  
 

RANGE CHANGE PROCEDURE (AUTOMATIC VEHICLES ONLY) 

Neutral must be selected on the main transmission before requesting a range change and then select the appropriate 
gear following completion of the range change. During the range change the main transmission will be locked in neutral. 
 
If neutral is not selected when a range change is requested then the request is denied and the driver will be advised to 
select neutral via the instrument cluster message centre (if fitted).