Transmission

Evolution of the Porsche "Automatic" Transmission from Sportomatic to Tiptronic To PDK

“Automatic gearboxes” in Porsche sports cars are nothing new. Porsche successfully campaigned a 911 Sportomatic to victory in 1967, driven by Vic Elford at the Marathon De La Routewith. Although not truly an automatic transmission, Porsche introduced the Sportomatic in 1968, sharing its basic design and operation with the “Automatic Stickshift”, or Autostick, from the VW Beetle and the NSU Ro 80. Besides no longer having a clutch pedal, those who have driven a Sportomatic are familiar with its quirky nature and the fact that you can’t rest your hand on the shifter since there was a set of contact points within the shifter would electromechanically actuate the clutch using a vacuum servo. Drivers still are required to “row” through the gears, four speeds in early models and three speeds in later years, coupled to a torque converter. This allowed drivers to leave the car in gear when coming to a stop and a higher lockup speed for the converter actually made models with the Sportomatic faster than their manual counterparts. The Sportomatic also proved itself to be durable with additional engine oil cooling being the only common modification required, as Porsche chose to use the engine oil as hydraulic fluid for the torque converter, resulting in higher oil temperatures, especially in hotter climates and in stop and go traffic.

The Sportomatic was available through the 1970s and even found its way into some 914s, before being phased out by 1980, leaving no “automatic” option for 911 buyers. It wasn’t until the introduction of the 964 and the Tiptronic that an automatic transmission found its way into 911s again in the 1990s. The ZF supplied “Tiptronic” was a fully automatic transmission. What makes the Tiptronic special is the software brain. Where most automatic transmissions in that era had little to no computer control, relying solely on a vacuum modulator for the transmission to determine load and gear selection, the Tiptronic monitored throttle inputs, engine and road speeds, ABS, and fuel delivery systems. The computer could “adapt” to driver style with five shift programs. A manual mode, and later steering wheel mounted shift buttons, allow the driver to manually shift the automatic gearbox. Like with any fully automatic transmission, keeping the ATF, or automatic transmission fluid, cool and clean is key to long life for these gearboxes. Fluid and filter changes on street driven cars every 36,000 miles ensure a long life, even when paired with increased horsepower from performance engine modifications. Porsche utilized the ZF supplied Tiptronic though 2008 in the Boxster, Cayman, and 911 and 911 Turbo models through the 997 utilized a very robust Mercedes supplied automatic capable of supporting the increased output of the turbocharged engine.

While the Tiptronic was not developed for racing or campaigned by Porsche, their efforts were redoubled on development of the next generation of automatic gearbox. The PDK was born on the race circuit in the 1980s while Porsche was campaigning the 952 and 962, eventually securing a win at Monza in 1986. Early prototypes were fitted to production vehicles and in 2009, Porsche introduced the Porsche-Doppelkupplungsgetriebe, or PDK transmission, in Boxster, Cayman, and 911 models. The PDK is a dual clutch transmission similar to gearboxes used by other manufacturers. Besides being able to shift faster than any human with rev-matching to boot, the PDK offers improved efficiency exceeding that of a manual transmission. Even though improved fuel economy helps Porsche as an automaker meet ever more stringent fuel economy and emission standards, the PDK was born on and for the race track. The PDK as used in street models have found their way into race cars, proving their durability and reliability. Case in point, the Cayman GT4 Clubsport utilizes a six speed rather than seven speed PDK along with different software optimized for race-only use, and even the Cup car is offered in PDK trim.

Like in a conventional automatic transmission, the dual clutches have their own hydraulic fluid as goes the differential which is lubricated with gear oil. In the 987.2 and 997.2, the PDK-side used a heat exchanged to cool the hydraulic fluid for the dual clutches. It was not until the 981 and 991 that a gear side cooler was also added to provide cooling to the gear oil.

Even with these improvements and more frequent servicing, tuners and race shops have turned to the aftermarket for solutions to beef up the PDK for track use:
 

• Guard Transmission offers a more durable limited slip differential than the one fitted by the factory that is known to wear out prematurely.
• Cobb Tuning PDK software for all models fitted with the PDK gearbox provides increased shift firmness, clutch pressure, and shift points.
• Joe Gibbs Racing Driven DCT dual clutch transmission oil fights shearing and viscosity loss, while providing superior performance over OEM fluid.
• Bilt Racing Service offers innovative solutions and upgrades for improved gear and PDK cooling including a billet aluminum PDK oil pan that features a modular filter and additional cooling.

With a decade of street and race experience, we now know with the PDK that Porsche has given us a robust transmission that outperforms any previous manual or automatic gearbox and does so while being nearly bulletproof. Porsche’s fastest models come standard with this amazing dual clutch gearbox, and although some purists will only accept a manual gearbox, love it or hate it, the PDK is here to stay and we are huge fans of the PDK. In street use, regular fluid and filter changes every 36,000 miles is a safe interval to provide a long life for the PDK transmission. In track use, added cooling and much more frequent fluid and filter changes are required to ensure the longevity of the PDK gearbox.