The clutch packs connect each rear halfshaft to the rear
drive unit when engaged. The clutch packs manage the
car’s front/rear torque split and control the side-to-side
torque distribution on the rear axle, delivering torque
vectoring capability that has a dramatic impact on
handling and cornering stability.
A maximum of 70% of the drive torque can be diverted
to the rear axle, with up to 100% of available torque at
the rear that can be sent to each rear wheel. This ensures
optimum vehicle stability, counteracting 'Understeer'
and initiating controlled 'oversteer'.
The rear drive unit does not require any normal
scheduled maintenance. The system is electronically
monitored and any required service messages appear in
the information display.
The rear drive unit lubricants may require changing if
the vehicle is subject to extended periods of high speed
driving, for example race circuit use.
A wide range of sensor signals is processed at 100 times
a second by the AWD system to adapt the torque
distribution to the respective driving situation.
This includes the following data:
•
Steering input
•
Mixture control
•
Engine power output/engine speed
•
Yaw rate
•
Lateral and longitudinal acceleration
•
Brake system data
•
Wheel speed
•
Temperature
AWD System Messages
When a AWD system fault is present, a message appears
in the information display and the system defaults to
front-wheel drive. If a warning displays, the vehicle
must be checked as soon as possible.
Action and Description
Messages
Appears in the information display if the all-wheel drive system overheats and
defaults to front-wheel drive. This may be caused by operating the vehicle with an
incorrect wheel or tire installed or excessive wheel slip and the system is over-
heating. The system resumes normal function and the message clears after the
correct wheel or tire fitted or after the system has cooled. To resume normal all-
wheel drive function as soon as possible, stop the vehicle in a safe location and
switch the engine off for at least 10 minutes.
AWD OFF
Appears in the information display along with the powertrain malfunction warning
lamp when the system is not operating correctly. Have your vehicle checked as
soon as possible.
Check AWD
Appears in the information display when the power transfer unit or rear drive unit
lubrication requires changing. The power transfer unit or rear drive unit lubricants
may require changing if you use your vehicle for extended periods of high speed
driving, for example race circuit use.
Driveline Oil Minder
Operating With Mismatched Tires or Wheels
NOTE: Only use replacement tires and wheels that are
of the same size, load index, speed rating.
NOTE: Using a tire or wheel that is not recommended
could cause steering, suspension, axle, power transfer
unit or rear drive unit failure.
The Focus RS does not have a spare tire. It is not
recommend using a mismatched tire or spare wheel,
however in an emergency, the system can tolerate a
mismatched tire or spare wheel of a different size to the
original for a short journey.
The system may automatically enter front-wheel drive
only mode to protect driveline components if a
mismatched tire or spare wheel is installed and a
message displays in the information display. The
message turns off after the correct wheel and is installed
and the ignition is cycled.
Major mismatched tire or wheel sizes between the front
and rear axles, for example 18 inch low profile tires on
the front axle and 20 inch low profile tires on the rear
axle causes the system to default to front-wheel drive
only mode.
53
Service Training
Four-Wheel Drive Systems
Lesson 3 – Powertrain
