The G64 gearbox is fundamentally similar to the G50 used in the Carrera 2 and consists of an integral transaxle unit where both gearbox and final drive reside in the same casing. The major difference is the integration of a torque transfer unit - the centre differential - at the forward end of the gearbox to provide the drive to the front differential to provide four wheel drive on the Carrera 4. Depending on application there are a range of gear ratios used giving rise to three variations of the gearbox as shown below:

The G64/02 transaxle was used for US cars only up until 1992 whereupon the standard G64/00 was used. Traction control is provided on the 4WD cars by an electronically controlled, hydraulically operated mechanical clutch system which is able to lock the rear and centre differentials in response to accelerometer sensors fitted within the car. This system is designated Porsche Dynamische Allrad Steuerung (PDAS for short). The oil used in the gearbox/final drive is SAE75W/90 Gear Oil - 3.8 litres for all Carrera 4 models.

A valuable note for the DIY'er is to make sure you can release the level plug BEFORE you drain the oil from the transaxle. If the level plug is seized, once the transaxle is drained you will not be able to refill it.

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