BMW 325i Sedan Product Information page 39

Torque flow with xDrive:
Black arrows represent
direct flow from transmis-
sion to rear differential;
gray arrows represent
modulated flow via multi-
disc clutch and roller
chain to front differential.
Front differential
Front halfshaft
xDrive system, shown here
on another BMW Series, is
in a transfer case directly
behind the transmission.
Drive proceeds from there
directly to the rear wheels,
and via chain to the front
driveshaft.
xDrive: BMW's new"intelligent"
all-wheel drive system
(325xi & 330xi models, available as of 9/05
production)
Benefits
• Excellent traction at all times, especially
• Optimum handling agility
• Surefooted, neutral handling in curves
When the "xi" models go into production in
September '05, they will incorporate BMW's
new, advanced xDrive all-wheel drive and
traction system. xDrive replaces the earlier
AWD system used in E46 325xi and 330xi
models, which employed a center differential
with essentially fixed front/rear torque split.
Instead of the center differential, xDrive
operates as follows:
• Driving torque is always transmitted to the
• The portion of torque transmitted to the
Transfer case
Front driveshaft
noticeable on slippery road surfaces
rear wheels, and most of the time to all four
wheels.
front wheels is controlled by a multi-disc
clutch that can be fully open, fully engaged
or at any level of partial engagement in
between.The torque split between rear and
front wheels is thus steplessly variable.
From
transmission
Roller
chain
To front differential
Rear driveshaft
• Engagement pressure on the multi-disc
clutch is directed by an electronic control
system in response to actual road and
driving conditions.
xDrive doesn't just optimize traction; it can
also enhance both agility and stability on
grippy as well as slippery road surfaces. Via
the same type of logic that DSC employs to
recognize and correct for excessive over- or
understeer, xDrive adjusts the front/rear torque
split to avoid these tendencies. If undesirable
oversteer is sensed, the multi-disc clutch is
completely closed, sending the maximum
possible torque to the front wheels. If excess
understeer is detected, xDrive opens the clutch
completely, sending no driving torque to the
front wheels. In the BMW tradition, the driver
enjoys optimum vehicle dynamics under a
wide range of driving and road conditions.
17 – Due to low-profile tires, please note: Wheels, tires and suspension parts are
more susceptible to road hazard and consequential damages.
Multi-disc To rear
clutch differential
Swash plate
& servo
motor
Lever
mechanism
Rear halfshaft
Rear differential
37