· 61 ·
The 911 | Transmission
In com parison with a viscous
multiplate clutch, where clutch
regulation is not initiated until
there is a difference in speed
between the front and rear axles,
the ele ctronically controlled
multiplate clutch responds much
more rapidly. Through continuous
monitoring of driving con ditions,
the ele ctronics are able to
respond to a v ariety of situations.
Sensors check, among other
variables, the rotation speeds of
all four wheels, the longitudinal
and lateral acceleration of the
vehicle, an d the steering angle.
By evaluating the sensor da ta,
the system can quickly adjust
the di stribution of drive force to
the fr ont axle in order to achieve
optimal balance. I f the rear
wheels threaten to spin under
acceleration, a greater proportion
of drive force is s ent forward
by a more powerful engagement
of the multiplate clutch. At the
same time, ASR prevents the
rear wh eels from spinning. When
cornering, the front wheels only
ev er receive as much drive force
as is necessary to prevent l ateral
instability. On unev en surfaces,
th e rear differential fitted
as standard to all-wheel-driv e
models, in co mbination with
ABD, also improves traction.
In this way, PTM, in con junction
with Porsche Stability
Management (PS M), ensures
that the perfect distribution of
drive is achieved every time.
PTM re ally comes into its own
in wet conditions or in ice and
snow. In these conditions, the
car’s acceleration capability
is simply breatht aking.
The result: a high level of safety
and outstanding performance .
Put to use in the most
intelligent way.
Mechanically locking
rear differential.
A mechanically locking rear
differential is standard in the
911 all-wheel-drive variants
a nd is available as an option
for all other 911 models in
con junction with 19-inch wheels.
It further enhances traction at the
driven rear axle on uneven roads
and when accelera ting out of
tight curves. This is acco mplished
by the d amping of load-change
reactions du ring fast cornering.
English 
