fluxdon

Hi Rennlisters

I'm having an issue with my newly acquired 2009 997 Carrera S equipped with the PDK transmission (48k miles on the car) . When I apply or release the throttle, I'm experiencing a noticeable clunk or jerking sensation. This happens at all speeds, but is most pronounced around 4,000 rpm or above. In general the gearshift are pretty smooth on the upshift.

I've (and AI) done some research, and it seems this could be caused by a few different things:

1. Worn or failing PDK clutch packs - The PDK transmission uses multiple clutches that can wear over time, leading to jerky engagement and disengagement of the gears.

2. Transmission fluid issues - Low fluid level or contaminated fluid in the PDK can cause shifting and throttle response problems.

3. Faulty engine or transmission sensors - Malfunctioning sensors that monitor throttle position, engine rpm, etc. can confuse the PDK's control module.

4. Mechanical wear in the drivetrain - Things like worn CV joints, differential issues, or other driveline components could be the culprit.

Has anyone else experienced similar symptoms with their 997 Carrera S PDK? What did you find to be the root cause and how did you resolve it? Don´t worry, of course I will take it to the workshop I just wanted what it potentially could be. I'd greatly appreciate any insight or recommendations, as I want to get this issue addressed before it potentially leads to more serious problems.

EVOMMM

First these issues could have been picked up at the initial PPI
now that you own it without a good inspection your stuck
first try a pdk flush at the dealer about $1500 hopefully that corrects the problem

wjk_glynn

At only 48K miles, I’d be kinda surprised if it were these. But it could be worn engine and/or transmission mounts.

As you noted, have a reputable Porsche shop first inspect it, and see what they come back with.

Bruce In Philly

2009 C2S 197K miles

In the PDK, there is a... um... forget what it is called... a multi-plate disc that is designed to cushion the grab of clutch packs (this is not a clutch)... that can fail. The way it works is that both plates are locked but provide resistance to the other as it moves somewhat to when both disks hit their limit and lock to each other. This is not clutch action as the rotation is limited and locked in that it can not spin. If the cushioning fails, you get a shift or throttle transition clunk. If this is the problem, it is repairable but only through and Indy who specializes on PDK repair. The dealer can only replace the PDK. Are you under some warranty? Was the car tracked?

Where do you live? On the east coast, a real PDK specialist is Atlanta Speedwerks... a race shop that not only repairs PDK, but beefs them up for racers. Yes, PDK will wear out if you are a track rat.

https://www.atlspeedwerks.com/

I attended a PDK workshop at their site last year and here is their video from that day... long, but covers what I noted above and all other PDK failure modes... there are many. They did denote that failures are rare, but noted that if you track your car, you change the statistics.... it is a machine and has limits.

https://www.atlspeedwerks.com/pdk-transmissions


Peace
Bruce in Philly (now Atlanta)

Thomas_

Edit: I had the clunks as well, when releasing the throttle quickly or hitting the throttle hard when rolling in gear. This is remedied now, read on.

Here is my experience, a copy of a post i did on facebook a few months ago.

Is your PDK jerking in downshifts in sport mode, or have a clunking or thud sound when shifting from P, D and R when stationary? If so, then read this… mine did, and here’s what I have done.

Car is a 2011 C4S PDK. I experienced rough shifts from time to time, and it seemed to get slightly worse over 1-2 years. Jerky downshifts, and seems it is only when in sport and with full auto shifts. It is like the car gets jerked forward a little bit when it downshifts. This happens also when going slowly e.g., 15-20 km/h and going to a full stop slowly – the car is rolling to a stop and when it shifts from 2-1 the rough gearchange and jerkiness is experienced some of the time, but not always. This behavior is observed also when driving more spirited and going from 4-3, 3-2 etc.

My Porsche has the original Porsche Approved guarantee, so any malfunctions in the driveline is covered by Porsche. I have had the car looked at several times at the Porsche service center. They can’t find anything wrong, no codes or anything showing signs of wear etc. But they can feel and reproduce it. I also experienced a clunk from the gearbox when shifting the PDK from drive to reverse and back to drive or park, sometimes loud, sometimes just slightly loud, and mostly nothing to observe. This they also acknowledged, and that this was not normal behavior.

What has been done to remedy this: Full PDK oil service, no change observed. Full PDK gear calibration, no change observed. Changing the motor mounts, this eliminated 80-90 % of the jerkiness/roughness. The motor mounts looked fine, just a slightly wear. The jerkiness probably was from the motor and gearbox shifting a few cm forward when downshifting because of the motor mounts bushings being too loose. I can’t explain why changing the motor mounts would have this much of an effect otherwise?

Porsche says that what roughness remains is how it should be, and how any other 997.2 PDK behaves. I tend to agree, it is much better. I sometimes still feel it somewhat, but it is much less abrupt and hard, and I probably wouldn’t notice, if I didn’t dive into this rabbit hole for a year trying to fix this.

I have a thesis that what somewhat remains is related to the PDK gearbox mount. As with the two motor mounts, the bushing/rubber in the PDK mount can get old and soggy. And if the motor mounts have been too loose for a time, then a lot of extra loads has been put on the PDK mount/bushing, so it might need changing as with the motor mounts. Unfortunately, Porsche can’t change the PDK mount/busing as a standalone part, this will require a new PDK gearbox from Porsche, as the PDK mount is not serviceable (from Porsche official that is).

As the car now is as any other 997.2 PDK per Porsche inspection, I will wait till the Porsche Approved guarantee is gone in about a year (car is 15 years old then and Porche Approved can’t be renewed) and then get the PDK mount/bushing/rubber changed, as there are other producers of this part, and it can be changed without changing the whole PDK gearbox. It is this bushing, that probably needs changing: https://www.design911.co.uk/p/gearbo...s-9a137505502/

Anyone else have the jerking feeling in downshifts in sport, or have a clunking or thud sound when shifting from P, D and R when stationary? what have you done to fix this? Or have you had the PDK mount bushing changed?

fluxdon

You are absolutely right, I do still have a slight warranty on the car so not all hope is lost. Good tip with the flush, I am though more and more in doubt if it is the PDK.

fluxdon

So many good tips from you guys, rennlist members are the best.

I am more and more in doubt if it is the PDK, or something else. I tried giving it the beans yesterday and don’t really experience any issues except when you are in the high end give it a hear more then it jerks a bit where I would expect that to happen only near the redline.

Car has only been driven 3k miles in the last 4 years (serviced by official Porsche dealer every year). Having a car standing still for so long should not be good for bushing right?

Also, I have noticed a couple of times that when I sad in the car before starting it, there was a loud clunk. Like something falling into place if that makes sense.

I am living in Denmark, so very far from US.

Have never experienced a clunk when putting the gear into drive, park, sport etc.

Thomas_

I'm from Denmark as well. See private message.

Rig.Stunts

Changing the motor mounts is cheap and easy . . .

BillB128

I'm with Thomas and Rigs. If the service records don't show that the motor mounts have been changed, it might be a good starting point.
The motor hangs from these mounts, so even if your car only has 48K miles, those two mounts have been holding up
the motor for 15 years.......

Here's a good video regarding replacement. It is an easy job.