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porsche hangout How Does The Porsche PDK Transmission Work?

Ah transmissions… A bit of a sore point with the performance motoring community is whether stick shift is better than automatic. To understand the PDK transmission, we are going to look at both types and answer that age-old question, is it possible to have your cake and eat it?

What’s In A Name:

Before we launch off into the deep end of automatic transmissions, we should probably discuss what PDK stands for. It is an acronym for the German word, Porsche Doppel Kupplungs getriebe (which is written Porsche Doppelkupplungsgetriebe). What does it mean? Directly translated, it means ‘Porsche Double Couplings System,’ which abstracted means Porsche dual-clutch transmission. Phew, German lesson is over for today.

Downshift To Sticks

Getting back to our original debate, the stick shift transmission is just about dead. There are increasingly fewer new vehicles that can be bought with a stick. Take Subaru, for example. They stopped producing stick shift Foresters way back in 2019.

However, there are purists who will argue that driving for them means being in total control of the vehicle. They refuse to let a computer decide what gear to select. There is some merit in their argument. Computers these days are better than good, but they still cannot grasp the entirety of the driving environment. (Tesla autopilot accidents, anyone?) Here, a skilled driver with a manual shift may have the edge on an auto box.

The Venerable Automatic

The problem with many drivers today is that their idea of an automatic transmission isn’t far off the initial designs the GM started using in their World War II tanks. Yes, automatic transmissions have been around almost as long as their stick shift brothers. Although instead of using a clutch, a standard automatic will use a fluid (called a viscous coupling) in its place. (We’re aware there’s also the CVT or continuously variable transmission, but we aren’t discussing it here.)

Anyone who has been stuck in traffic knows the benefits of an auto over a stick. You don’t have to continually clutch and shift up just to shift back down. In traffic or cruising at interstate speeds are where an automatic more than makes up for its sluggish shift and extra gas mileage.

Enter the PDK

By now, you should have a clear picture of both types of transmission and their respective drawbacks. It was clear to Porsche that a clutch system was much snappier than the viscous coupling used by all other automatic transmission manufacturers.

In the 1960s, they asked what seems to be an obvious question, can’t we automate a stick transmission? Understandably the computer technology required to do this only really strengthened in the 1980s, but they never lost sight of the idea.

A PDK transmission is essentially an automated stick shift with one major difference. It has two clutches. Why? Well, consider the same system only using one clutch. The computer must clutch in, select the gear, then clutch out. Let’s assume each of these steps take a second. That is three seconds to change gear! Your average human being will do this in one. This shift time factor is the bane of all other automatic transmissions.

By having two clutches, the PDK always has two gears ready. The one which is engaged and its runner up. Porsche has structured this by assigning one clutch to the odd gears and another to the even ones. The clutches run one inside the other concentrically. Returning to our original assumption, a shift would only take a second. (In practice, this is much quicker.)

It hasn’t been all smooth roads for the PDK since its first introduction on the 911 997. Understandably whenever you introduce a new technology, there will be speed bumps (or rebuilds). If there is anything Porsche excels at, it’s refinement. They stuck to their guns, giving us the silky smooth PDK we know today. There really can be the best of both worlds, and the only reason left to choose a manual transmission now is a personal preference.

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