Bradym6

Hey guys looking to see if you have experienced this and if it is considered normal. I recently purchased a 09 c2 cab PDK w/42k. Absolutely love the car as it is a blast to drive. PDK seems to shift smooth however I have noticed one thing that may be concerning.


When starting from a dead stop I would say 5% of the time it seems as if the clutch slips out of 1st and then back in (RPM jumps up a little bit and you clearly can feel no gear is engaged). It isn’t harsh when is slips back in as I haven’t noticed this when really pushing it off the line. I also have noticed it in reverse. It ONLY has happened when starting from a stop.


Has anyone experienced this in their PDK and do you have any technical idea what is happening?


I have searched endlessly on this only found one short thread from 2010 that 1 person said “yeah I have had it happen” and that was it. Any help or insight would much be appreciated!

OKB

youll find it a little jerky on soft starts or on hills its worse , it can be smoothed out by leaving it in S mode or if you get a ecu software you can have the idle rpm raised and that cuts out mostly

Bradym6

Thanks for the response. It doesn't seem jerky to me it literally is like shifting the car to neutral and then back into gear all in about a 1/2 second when starting off. You can definitely feel the clutch disengage and reengage in a split second (you can feel gear engage as you slightly move forward from a stop and then a split second you are not moving forward and the rpm jumps a little then it finds the gear again). I wouldn't be as worried if it did it every time but again it only happens maybe 5% of the time.

BTW I did have the DME scanned and it came back with PDK fault codes:

u0418 CAN fault, brake

u0146 CAN timeout Gateway

u0155 CAN timeout instrument cluster

The Porsche shop said that this is normal after a battery change and to not worry about it and cleared them away.

ADias

Have you done a proper PDK service? Clutch oil and gear oil change?

speedracerf4i

Was that 5% of the time during a hill stop?
If so, then it may be the automatic hill brake disengaging.

During a hill stop, the brake will stay engaged for a second or 2 after you release the pedal or step on the accelerator to reach a pre-determined RPM. Once you apply the accelerator, the first 0.5 s will not give you any forward momentum because it has to overcome the brake.

I don't think it should matter whether you have a manual or PDK car. They all work the same.

"The hill-hold function became standard for Porsche when single- and dual-clutch transmissions like the Porsche Doppelkupplung (PDK) transmissions found their way out of their racing vehicles and into street cars. Although shifts feel automatic, inside the PDK is a full-blooded manual transmission with two computer-operated clutches, unlike a normal automatic transmission with a torque converter that connects the engine to the transmission and slips when at idle speed (and keeps the car from rolling back on moderate inclines). So, when the PDK-equipped car comes to a stop, the computer disengages the clutch, effectively putting the car into neutral – and if the car is on a hill (because it is technically a manual transmission) it will roll (either forwards or backwards). With the hill-hold function, the car recognizes if the car is going to roll and applies the brakes when the footbrake is released."

Bradym6

The transmission has not been serviced yet however it probably is due (my manual says 6 years or 60k whatever comes first) Correct me if I'm wrong but im under the impression that the clutch oil gets changed at 60k/6yr and the trans oil is 10 years or 100k.

Ive actually never had it happen when on an incline, its only been backing out of a flat parking spot or pulling off at a stop light.

ADias

I'm in favor of changing both clutch and gear oil and do it every 5 years.

ltcjmramos

OT: Have you had this done? Wayne and I are getting different stories from service (indy and dealer) about what needs to be done, (is there a filter involved?), and varying dollar estimates for the service.

ADias

I do all my work at Fletcher Jones (Fremont) under Gunter's guidance. I did the service at 5 years, as I prefer to change oil before its recommended life. I do not recall a filter, but there may be one. FJ has done this many times and yes I have heard stories about other dealers. I would never trust a PDK to an Indy, certainly not at this point.

ltcjmramos

Ah, the famous Gunter. Do you recall what it cost?

(Got your PM.)

1990nein

--

Wayne Smith

The clutch plate gap can be adjusted to improve on this. You need to slow to a stop from about 15 mph. Leave it in drive and wait a couple of minutes. You will hear or feel a slight disengage of the clutch plates. Then slowly accelerate to 15 mph and repeat. As you start, the gap is measured and adjusted. The start will be rough, but it will improve after enough iterations.

When mine is cold it may start harshly. It takes time for the oil to circulate.

Hill hold can be a factor and I have found that it doesn't take a lot of hill.

Mine will sometimes try to stay in 2nd when starting (fuel economy) and this can be rough, especially if it second guesses itself and down shifts in the midst of starting. I generally shift manually and make sure my starts are always from first gear.

The PDK is sold as an automatic, but it really prefers to be treated as a clutchless manual. I generally run Sport Plus with manual shifting (not much point in running near red line during DD). This gives the best of all worlds IMHO.

The car is not meant to stop. You are supposed to be driving. That's the biggest problem ... find endless roads full of curves and never get below second gear! If you must stop, allow a bit more throttle for a more aggressive start. This will smooth things out. Just leave yourself enough space to do this!

Bradym6

Thanks everyone for the suggestions and input. I think I will first try the start stop tactic to try and adjust the clutch plates. I called the dealer to get prices on a clutch fluid change and they said "it doesn't need to be changed until 120k so don't worry about it." I told them I read the owners manual and it said to do it at 6 years or 60k and their response was "those manuals aren't car specific" hmmmmm

The strange thing is it doesn't happen consistently. I could see if it happened 95% of the time it would just be how the PDK is engineered and assume there was some learning curve for the PDK system. Unless I am doing something different when I am pressing the gas to make it occur I'm at a loss. The next time it jumps out of first gear I'm going to hit the gas and see how hard it engages when going back into gear.

Wayne Smith

PDK =

We're just hitting 6 years on the PDK cars. Most of these cars are well below 60K miles. Most dealers have not done routine maintenance on the PDK yet (6 years or 60K miles).

My local dealer has not been able to give me a PDK oil change price on several occasions and then gave me $400 one time and $1800 another time. The last time I sat with the SM the price changed three times during the conversation and I could not be told if there was a filter involved or not. However, he did tell me about the clutch adjustment procedure.

After changing the (MT) transmission oil for a friend the result was a much smoother gear change. I'm hoping for this when I change my PDK oil. But in this case we are talking apples and oranges ... wet clutch oil, not transmission gear oil ... or are these shared? Another thing my dealer was not sure about!

Wet clutches, transmission gears, differential, all wheel drive controller, front differential, overlap of terms! About the time I think I know this stuff, somebody says something that makes me wonder if I'm crazy! And I used to wrench for a living!!! I must be over thinking this.

This is about experience and goes to factory training, or a lack thereof. I am disappointed that my local support offers me little hope, but I believe it is Germany who has dropped the ball here.

I'm past 62K miles and need to have the PDK oil changed. The manual states I should change the all wheel drive controller oil (local dealer did not know this) and flush the "lifetime" coolant. The transmission oil comes at double the time / mileage. I'm inclined to do them together.

There is a dealer much further from me that may know more. But my schedule has been rough and I'm not sure when I will make it there.

All I can say is ... do your homework. All I can ask is ... post your results. I am sure there are many watching this post looking for answers as well.

Good luck.

Yet anothercrisis

I have the same "slippage" between 1 and 2 in either sport or normal modes. It happens only the first gear change after the car is warm then shut down for about 5 minutes. This happens to me routinely on a grocery run so it does the same each time. Only one time though. Next change is normal.

I took it in for the final service before warranty ends and of course the dealer service claimed to be unable to duplicate. I immediately bought extended warranty coverage!
2012 C2s 18k miles.