· 61 ·
The 911 | Transmission
In comparison with a viscous
multiplate clutch, where clutch
regulation is not initiated until
there is a difference in speed
betwee n the front and rear a xles,
the electronically cont rolled
multiplate clutch responds much
more rapidly. Through continuous
monitoring of driving c on ditions,
the electronics are able to
respond to a variety of situations.
Sensors check, a mong other
variables, the rotation speeds of
all four wh eels, the longitudinal
and lateral acceleration of the
vehicle, and the steering angle.
By evaluating the sensor data,
the system can quickly adjust
the distribution of drive force to
the front axle in order to achi eve
optim al balance. If the rear
wheels threaten to spin under
ac celeration, a g reater proportion
of drive force is sent forward
by a more powerful eng agement
of the multiplate clutch. At the
same time, ASR prevents the
rear wheels from spinning. When
cornering, the front wheels only
ev er re ceive as m uch drive force
as is necessary to prevent lateral
instability. On uneven surfaces,
the rear differential fitted
as stan dard to all-wheel-drive
models, in combination with
ABD, also improves traction.
In this way, PTM, in conjunction
with Porsche Stability
Management (PSM), ensures
that the perfect distribution of
drive is achieved every time.
PTM really comes into its ow n
in wet conditions or in ice and
snow. In these conditions, the
car’s acceleration capability
is simply breathtaking.
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 re ar
differential is standard i n the
911 all-wheel-drive variants
a nd is available as an option
for all other 911 models in
conjunction with 19-inch wheels.
It further enhances traction at the
driven rear axle on uneven roads
and when accelerating out of
tight curves. Th is is ac complished
by the damping of load-change
reactions during fast cornering.
English 
