C o m p l e t e  9 6 4

Drivetrain

GENERAL-

The G50 gearbox that had been recently introduced (1987) on the Carrera 3.2 was also utilised on the 964. The gearbox and associated clutch mechanisms were a far improved unit when compared with the gearboxes utilised on the earlier Carrera 3.2's.

Perhaps the most significant change was the addition of a dual mass flywheel (produced by Freudenberg) in 1990 to both the Carrera 4 and 2, that was in theory supposed to smooth out torque output when pulling at low engine speeds hence removing gear chatter from the gearbox. Unfortunately, the long term viability of this dual mass flywheel proved less than reliable, and was subsequently replaced in the Carrera 2 by a new flywheel produed by LUK in 1993 (such flywheel can be retrofitted to earlier Carrera 2's with ease). However, due to different torsional frequencies, the Carrera 4 maintained the original Freudenberg dual mass unit to eliminate unnecessary vibration.

THE 4 WHEEL DRIVETRAIN-

The four wheel drive mechanism of the Carrera 4 also utilised a variant of the G50 gearbox (G64), although this obviously had to be significantly adapted to drive the front wheels of the Carrera 4. The front differential housing was linked to the gearbox via a large diameter tube that (through the gearbox's hollow secondary shaft) connected to an epicyclic differential at the front of the gearbox. From there, the drive moved to the rear differential via a shaft passing through the hollow secondary shaft. The front/rear torque split was maintained at 31/69% through the central differential. This central differential wais in turn controlled by a "multiplace clutch" that could  automatically actuate whenever wheel spin was identified by the ABS system. The clutch would then provide excess torque to the axle with the "better grip". A similar electronically controlled rear differential would act as a normal differential (split drive between left and right rear wheel) as well as intervene whenever the accelerator was released while cornering, in order to minimise the accelerator pedal off oversteer tendency of the 911. As a result, the Carrera 4 was a far safer car for the inexperienced driver when compared with the Carrera 2- which was however deemed to be the better experienced drivers car. Indeed if an experienced driver were to take a Carrera 4 and a Carrera 2 onto a race track, the Carrera 2 would almost always be faster. The converse is obviously true of an inexperienced driver, who could find himself in a significant amount of trouble without the aid of the four wheel drive.

TIPTRONIC-

In 1990, the 964 Carrera 2 was offered with Porsche's first fully automatic transmission (the Tiptronic). The transmission also permitted the manual selection of gears up to a point- if and when a gear selection was thought to be harmful by the electronic system, the transmission would not allow such a shift. For example, the transmission would shift up when maximum permissible engine revs had been reached, or move automatically down when the engine speed had reached a speed incompatible with the gear selected. An interesting point of note was that the transmission would always select 2nd gear for a start, unless a sprint was required, at which point the driver could select 1st gear. The fully automatic mode was achieved by shifting the gear selector into the "D" position on the gear shift plate. Conversely, to select manual mode, the gear selector would have to be shifted to the right into the short lane with "+" and "-" selectors. From this gate, the four different gears could be selected "manually"- forward pushes would select higher gears, pulling back the lever would select a lower gear. The Tiptronic system, whilst extremely competent, remained a weak link in the Carrera 2 given that there were only four gears on tap. Performance obviously suffered with 100kmh being reached only after 6.6 seconds, as opposed to 5.5 seconds for a manual Carrera 2. 

Indeed, if five gears had been offered, it is most certain that an enthusiast would be far more likely to consider a Tiptronic equipped car for spirited driving. As was, the Tiptronic gearbox made sense for a large number of city dwelling 911 owners, who all too frequently got stuck in traffic. However, there were exceptional 3rd party supplied alternatives, such as the RUF E. K. S. system (to be described under Modifications).

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Note the left dial which is utilised to lock the 4 wheel drive mechanism on the C4 (the C2 has only one dial for the manual wing control).

The spiritual ancestor to the Carrera 4, the awesome Porsche 959.

Note the tiptronic gearshift in this 964 Carrera 2 coupe.

Tiptronic equipped cars had the details of gear engagement on the rev limiter.