Cactus

So this explains why the 911's are way more reliable. I always wondered this....

Petza914

Correct. Many fewer 911 PDK failures. Part of that's is numbers as there are many more Macans sold than 911s with PDK but part is also the difference in the transmission, but also the loads on them. The 911s are.lighter and don't tow anything compared to the Macans. It's also the reason they've never offered a PDK in a Cayenne, because it would severely limit the towing capability.

DIYDanCars

Also, 911 owners don't put anywhere near the miles on their cars as Macan owners do. My neighbor has been through two PDK transmissions on his 911 (under warranty) and he drives the car daily. His warranty is expiring this year and do you think he will be keeping the car? Nope!

Cactus

Wow...two?!

DIYDanCars

Yep. He calls the car his Golden German turd, meaning its super expensive to purchase and is very poorly built. He loves the way the car drives, but he won't be buying another one or any Porsche for that matter. He was really disappointed in the reliability of his $110k car which I don't blame him.

Cactus

Guess I'll just stick to my 993 and Toyotas.

Mufflerbearing

As asked before, how do these transmission issues exist in the newer 2020-2024 Macan Turbo/GTS cars? I bought a 2020 Turbo for my wife and I am looking at a 2023 GTS for me. We don't do any stop and go driving. Yes, we will have the transmission fluid changed on time.

VAGfan

It is not the excessive shifting that causes excessive transmission fluid temperature, it is the continuous "soft" clutch engagement during stop and go traffic.

I was observing the clutch hydraulic fluid pressures while driving in stop and go conditions, and one of the clutches is always slightly engaged (and slipping, causing fluid temperature rise, and clutch wear), even when the car is stationary. The only way to avoid this would be to shift into N, during long full-stop traffic situations. Sport Mode or manual shifting does nothing to reduce this clutch slip operating condition. This soft clutch engagment, while at a stop, is done to keep the power application smooth when you start moving again, effectively emulating conventional auto transmission torque converter "creep".

I was surprised to see this, as I assumed that both clutch pressures were zero, when the car is stationary in D.

RandyL

Interesting, and good info! Regarding clutch slippage, there is a clear and significant difference in the amount of slipping when accelerating away from a stop in Normal mode versus Sport mode (far less in Sport mode). Frankly, I consider my S almost undriveable in Normal mode and it's annoying that the drive mode is not retained at shut-down, we need to push the button every start. It's almost subconscious for me now, but still...

chassis

This simulates a traditional torque converter.

Petza914

I don't think that's true. It sounds like in the PDK that the physical clutch is actually slightly engaged and slipping and why that heats up the fluid and causes issues. In a torque converter transmission that creep is all done by fluid movement and no physical clutch contact. The lockup clutch engages at higher speeds eliminating slippage for a 1:1 drive ratio.

Here's a great video on how a torque converter transmission works -

VAGfan

The point is that the slight clutch engagement is done on-purpose to mimic torque converter creep.

Petza914

...but in a way more equivalent to slipping the clutch on a manual transmission car, which none of us would do. The torque converter does this with no wear, damage, or heat.just from fluid movement.

Larson E. Rapp

I have to assume the engineers aren't complete idiots. VAGfan, were you actually monitoring the fluid temperatures, or just monitoring the fluid pressures at standstill and assuming the temperatures are high as a result? Any graphs you can share?

VAGfan

I was monitoring the real-time clutch pressures, during some stop-and-go driving. I did not monitor the fluid temp, but I think the temperatures will start climbing if you are stuck in traffic, spending long periods in D, without the car not moving.
No, the engineers are not idiots, but making the dual-clutch smooth (by keeping the clutch slightly engaged, and slipping) before the driver releases the brake and starts accelerating is a goal of the transmission control software, to prevent customer complaints of "clunky" or "jerky" transmission behavior, as most people are used-to the smoother operation (and low speed creep behavior) of conventional automatic transmissions. The clutches are durable enough for some calculated average lifetime of clutch slip during stop-and-go traffic usage, but knowing how this transmission works allows us to shift to N, during long periods of stand-stills, to hopefully extend the life of the transmission.

Clutch slipping is the only thing that raises fluid temperatures. Changing gears doesn't create significant friction to increase the fluid temperature.