Originally Posted by curt3g

Hi all,

Yup, joined Rennlist in 2017 and this is my first post. Ever get distracted?

It looks like we may have joined the club of misbehaving PDKs. We have a 2015 911 GTS 4 with about 28k miles on it. No track time and has had regular maintenance. A couple of weeks ago, we got the dreaded ‘Transm. Fault, Poss. No R gear, Drive on Poss.’ message. The Durametric shows one fault - P1765 (gear disengagement lock). We parked the car until I could look into it. Started with Rennlist, and low and behold, this thread popped up. Have read it and followed the breadcrumbs to the ‘Chinese PIWIS clone’ thread, and then over to the ‘PIWIS 2 setup as a virtual machine’ thread on Planet-9.

I’ve got VirtualBox version 6.1.12 installed and the PIWIS VM file hooked up. The Planet-9 set of directions are spot on and it all seems to run fine on one of our new-ish laptops. I’ve been exploring around in simulation mode. Unbelievable. I’ve wanted this kind of capability ever since we bought the 2009 Cayman.

Next step will be to purchase a PIWIS II clone box / cable set. I’ve got a question on vendors, but will post that over on the PIWIS clone thread.

If I stumble across anything worth sharing along the journey, will gladly post.

As others have said already, a BIG thank you to PV997 for all of this work. And to everyone else that has added to it. What a resource.

Cheers!

Originally Posted by 991.1Turbo

Hello Dear Porsche enthusiasts.
Sorry if my sentence structure is not quite correct but I am from Belgium located in Europe. Forgive my typos.
I have been reading this topic for a while and I first want to congratulate you on your search and enthusiasm. I've been reading this topic for a few weeks now.
I'm Steve from Belgium and I've been the proud owner of a 991.1 Turbo with PDK for 2 years now.
At least, I was a proud owner because recently I also experience more and more PDK failures on a regular basis.
The symptoms I read from the various posters here are also reflected in my PDK failure.
As my Hobby describes the failure on his track day in post *134, I had to undergo on March 21 at Francorschamps. I was able to walk out of the track with all security features turned off by the computer itself. Engine feeling that only 2 cylinders were active. Arrived in the paddock, let the car cool down for half an hour and started again and all mistakes were gone. In the drive home, the PDK 1 x had a slipping feeling. Stop for a moment, turn off the ignition, turn on the ignition and continue driving as if nothing had ever happened. I also never get a warning on the dashboard.
If the PDK starts to fail with me, this is accompanied by the physical feeling such as the turbo pressure that fails and audible upshifting in the drive position, but visually the speed remains for a long time where no command can be given with the paddles on the steering wheel or not manually with the gear lever.
Bit frustrating as this is my dream car and I saved my life for it and when I read that replacing a new PDK is a heavy cost, I lose my courage a bit.
I myself have been a do it yourselfer all my life, I have always worked on my cars and motorcycles myself as I once obtained a diploma in car mechanics. So I do know something about a hammer, chisel and crowbar.
I changed all the oils last winter (December) because I hoped that the PDK failure would go away? Not so.
The PDK failure does not always occur. Sometimes it just comes in busy traffic where it is then very quiet driving (walking pace), with the flow of traffic, sometimes not at all. Very frustrating

Originally Posted by 991.1Turbo

Hello Dear Porsche enthusiasts.
Sorry if my sentence structure is not quite correct but I am from Belgium located in Europe. Forgive my typos.
I have been reading this topic for a while and I first want to congratulate you on your search and enthusiasm. I've been reading this topic for a few weeks now.
I'm Steve from Belgium and I've been the proud owner of a 991.1 Turbo with PDK for 2 years now.
At least, I was a proud owner because recently I also experience more and more PDK failures on a regular basis.
The symptoms I read from the various posters here are also reflected in my PDK failure.
As my Hobby describes the failure on his track day in post *134, I had to undergo on March 21 at Francorschamps. I was able to walk out of the track with all security features turned off by the computer itself. Engine feeling that only 2 cylinders were active. Arrived in the paddock, let the car cool down for half an hour and started again and all mistakes were gone. In the drive home, the PDK 1 x had a slipping feeling. Stop for a moment, turn off the ignition, turn on the ignition and continue driving as if nothing had ever happened. I also never get a warning on the dashboard.
If the PDK starts to fail with me, this is accompanied by the physical feeling such as the turbo pressure that fails and audible upshifting in the drive position, but visually the speed remains for a long time where no command can be given with the paddles on the steering wheel or not manually with the gear lever.
Bit frustrating as this is my dream car and I saved my life for it and when I read that replacing a new PDK is a heavy cost, I lose my courage a bit.
I myself have been a do it yourselfer all my life, I have always worked on my cars and motorcycles myself as I once obtained a diploma in car mechanics. So I do know something about a hammer, chisel and crowbar.
I changed all the oils last winter (December) because I hoped that the PDK failure would go away? Not so.
The PDK failure does not always occur. Sometimes it just comes in busy traffic where it is then very quiet driving (walking pace), with the flow of traffic, sometimes not at all. Very frustrating

Originally Posted by 991.1Turbo

how can we contact each other?:maïs:

Originally Posted by Hellga991.1

#1. The information in this blog that has been compiled over years and years is remarkable. The fact that PV997 still replies and still has advice after all these years is a testament. Thank you PV997!!!!

#2. My 991.1 has been in an independent shop for 2 months as they continue to exhaust avenues for a leaking PDK over replacing the entire unit. It's the same issue as sl430 was having back on 06-04-2020. We have no error codes, no lights on the dash, wouldn't even know anything was wrong if it wasn't for the small puddle of greenish fluid on my garage floor.

#3. Since the blog is so lengthy, I missed if the solution of plugging the bolt's hole was ever a success? This will stop the leaking, but the fluid that is coming from the hole of the bolt should not be accumulating in the chamber where the bolt is correct?

#4. Has ZF updated any of the previous known issues with the Replacement PDK transmissions for 991.1/2?

Thank you for your time

Originally Posted by PV997

Hi ​​​@Hellga991.1 , thanks for the kind words. Can you refresh my memory regarding the issue and which bolt you mean? Greenish fluid is a bit strange as the clutch fluid looks amber (like honey) and the gear oil is brown. Do you know which fluid it is?

Originally Posted by PV997

Introduction: This post documents what I've learned regarding PDK internals, parts prone to failure, access to those parts, where to get replacements, and generally how to fix a failed PDK yourself. After ten years in service Porsche still won't make this information available, instead insisting owners drop $15k to $20k on a replacement transmission. This post is aimed at those who refuse to accept this, and provide experienced DIY'ers the info needed to save themselves a boatload of money. Hopefully it can also be used as a resource for independent mechanics who are currently unwilling to service the PDK. I'll be adding new info to the post as it becomes available.


Original post
There was recently a post where a Rennlister sold his 997.2 GTS at a significant loss after his PDK failed. That post prompted me to document what I’ve found regarding PDK serviceability. Apologies for the length of this but I wanted to put it all in one place for reference.

I’ve had my 997.2 with PDK for few months now after switching from a 6MT. I was considering an extended warranty, mainly due to PDK replacement cost ($15k to $25k depending on the PDK source). There have been many claims that the PDK is not serviceable but must be replaced in the event of pretty much any failure (i.e. a disposable transmission). This is pretty frightening as items like solenoids fail all the time, like any other electro-mechanical device they wear out.

Fortunately, this just isn’t the case and this transmission is very repairable. Although this transmission is complex, it’s not overly complicated and is serviceable in many ways that aren’t readily documented (intentionally I’ve come to believe). Much of the work can be done DIY. I do caution that this info below has been compiled from my research and I can’t guarantee it’s 100% accurate, but I do believe it’s reliable. I welcome any comments or corrections.

A good animation of the PDK can be found in this video from ZF the manufacturer of the transmission. It gives background into the various aspects of the PDK’s operation that is helpful in understanding servicing the PDK:

https://youtu.be/cd10wif87Qk

For reference the PDK model used in the Carreras (and also Boxsters and Caymans) is a ZF model 7DT45. 911 Turbos use a ZF model 7DT70 which is identical to the ZDT45 except it has a heavy duty clutch, strengthened major components, and slightly different gear ratios. An excellent technical white paper from the manufacturer (ZF) can be found here:

https://link.springer.com/article/10.1007/BF03225047

Unfortunately it looks like this paper is now pay-walled. I found a copy of it in the wild and can forward to those interested.


PDK Repair

(Foreword: This post was written with regard to the 997.2 PDK but in almost all cases directly applies to the 987.2 PDK also. The PDK did see minor updates for the 991.1/981.1 in 2013 but is still generally the same transmission. These changes include addition of a gear oil pump and cooler, a gear oil temp sensor, sealed clutch updates, and the option for a true locking differential (including an additional solenoid and pressure sensor to engage/disengage). The 991.2 PDK introduced in 2017 is substantially changed and it's not clear how much of this info applies. The PDKs in the Panamera and crossovers are completely different units from that discussed here.)

The PDK has two separate chambers, the hydraulic section (red below) and the gearbox section (blue).



From scouring countless posts describing PDK failure symptoms, unsurprisingly the large majority of PDK issues occur in the hydraulic section. This makes sense as unlike other automatic transmissions, the PDK mechanical gearbox section is functionally equivalent to a manual transmission. In fact ZF refers to the PDK as an automated manual transmission and used this same gearbox on the 991 MTs. There's no series of planetary gears with corresponding clutches like a traditional AT, but gearsets, synchros, and shift forks just like an MT. Short of a catastrophic failure, there just aren’t that many things that will break in this gearbox. The hydraulic section and associated sensors are the weak link.

It's important to understand that the PDK transmission has no "smarts" of its own. All decisions are made by the transmission control unit (TCU) , a small computer that is located inside the vehicle. The transmission can only react to commands from the TCU and relay collected data back to the TCU. Commands are carried out within the transmission by the valve body (which engages the clutches and shifts gears) and data is provided by four different sensor types. These are very simple interfaces where components simply read or provide analog or pulse width modulation (PWM) signals, and all are discussed in detail in this post. Note that any type of software error, ROM corruption, or similar types of diagnosis pertains exclusively to the TCU and has nothing to do with the transmission. The distinction is critical as a new transmission is $15k or more whereas a new TCU is only $700 and easily accessible.



Valve Body, a likely suspect

The hydraulic section includes electro-magnetic actuators (solenoids) that regulate the flow of hydraulic fluid to control clutch and gear engagement when commanded by the transmission control unit. This seems to be the most prevalent failure location, but fortunately they are easily accessible and replaceable by switching out the valve body itself. (Porsche calls this an “electrohydraulic control unit” but anyone who’s ever worked on a transmission will know it as a valve body.) The valve body can be replaced by dropping the PDK oil pan and does not require transmission removal. It can clearly be seen in this photo below, the solenoids are the colored cylinders on the left side of the picture.





A PDK control unit fault code relating to accessing a specific gear (or inability to shift to a specific gear) is very likely a valve body solenoid issue. In addition, there are also electrical sensors within the transmission that monitor responses to solenoid action and report status to the transmission control unit. Sensor failures can also cause faults and are discussed later in this post.

New replacement valve bodies can be sourced directly from Porsche (~$1700 discount at Sunset Porsche, list is $2800), remanufactured units are available from China (~$850), and used units can be found on Ebay from dismantlers (~$500). This is a universal part for transmissions used on 911s, Boxsters, and Caymans. The 997.2 part number is 9G1.317.897.00 (for 2009-2012 Carrera, Turbo, and GT3).

There are also other identical looking valve bodies available from Porsche under part numbers that apply to different years: 9G1.317.897.05 (2012-2015 911), 9G1.317.897.010 (year unknown), and 9G1.317.897.35 (2012-2015 911 and 2014-2015 turbo/GT3). It’s not clear what the difference is between these units so it’s probably best to eyeball the existing valve body prior to ordering a new part just to be safe (the PN is on the bottom and can be seen by removing the pan). It looks like the part numbers rolled for later 911’s and that 9G1.317.897.00 applies to all 997.2 PDK models, but this is not absolutely certain. Note that 991 valve bodies include an additional check valve that is required for the autostart feature so it's important to use the correct part number.

The valve body is item 11 in this drawing from the 2010 parts catalog:







Links to the valve body sources:

New Porsche valve body: https://www.sunsetporscheparts.com/o...au-9g131701500

Chinese remanufactured valve body: https://www.shenghaiautoparts.com/sh...r-porsche-911/

Here’s a close-up shot of the bottom of the valve body:




And here’s the top of it, there is no gasket as far as I can tell. The wiring harness attaches at the slots in the colored solenoid caps.




Here’s the screw tightening sequence and the torque requirements. Important note: When removing the valve body from the transmission only remove the screws that are circled. The other screws hold the valve body itself together and should not be removed.





See the service bulletin attached to this post for more info on valve body R&R.

To make the repair even more inexpensive, an individual solenoid on the existing valve body can replaced rather than replacing the entire valve body. The PDK transmission uses solenoids from ZF, the manufacturer of the transmission. ZF uses a standard line of solenoids on many transmissions that are color coded to denote solenoid function and characteristic resistance. For example, here’s an individual “orange” solenoid from the PDK valve body, a standard ZF part.



These are the solenoid OEM part numbers, if you google the numbers or search Ebay they can be found for sale individually. Search around as the prices can vary wildly among suppliers, from as low as $40 up to $150.

• Orange (EDS type): 0501 214 958 (ZF OEM PN)
• White (EDS type): 0501 214 959 (ZF OEM PN)
• Black (MV type): 0501 319 037 (ZF OEM PN)
• Short orange (EDS type): TBD, still searching

As of June 2020 a Chinese aftermarket parts supplier now provides a full PDK solenoid rebuild kit priced around $235 for all eight solenoids. I don't know anything about the quality of these or their provenance, but if faced with a failed valve body I'd certainly give it a try. Here's the link and a photo:

https://www.shenghaiautoparts.com/shop/solenoids-kit/pdk-transmission-solenoid-kit-for-porsche/



As of July 2021 this kit is also showing up on Aliexpress for about the same price if you search around.

Here's a good drawing of the valve body showing the function of the solenoids and other various valve body components. This should be very helpful in troubleshooting and identifying malfunctioning components. Note that EDS1 (item 7) looks different from the others, this appears to be a pressure failsafe that enables clutch 1 engagement and "limp home" operation if needed.





The information below regards the function of the various solenoids in the valve body. This info was compiled from reviewing solenoid function with various ZF transmissions with publicly available documentation and refers to the designations in the drawing above. Some of the info below is supposition based on how ZF has implemented transmission control in the past, and it cannot be guaranteed as 100% accurate (prefaced with “appears to”).

The patterns noted below should be helpful in troubleshooting malfunctions that result in missing gears or shifting problems. Since a replacement valve body is $1700 whereas solenoids can be found for $50 it’s certainly worth more investigation.

Solenoid types – there are two different solenoid types used in the valve body, EDS type and MV type, all are controlled by the TCU

• EDS – this solenoid type regulates hydraulic fluid pressure over the range of 0 bar to 4.7 bar. Pressure regulation is either proportionate to the supplied current, or inversely proportionate depending upon the solenoid type
• MV – these solenoids are simply ON/OFF switches that either provide or remove hydraulic pressure within the system.

EDS4 (item 10 in the drawing above, note there is a misprint in the drawing above as EDS3 is shown twice) – This EDS solenoid regulates overall system hydraulic pressure. Pressure is built up by the clutch fluid pump, this solenoid regulates circuit pressure by bleeding some fluid back to the pan thus bypassing the valve body’s hydraulic system.

EDS1 and EDS2 (items 7 and 8) – These solenoids regulate hydraulic pressure to the two clutches. The clutch system is adaptive in that hydraulic pressure is varied to account for clutch wear over time. This is done by adjusting pressure within the clutch if the TCU senses slippage or otherwise slow engagement (monitored via the driveshaft speed sensor discussed later). There are two solenoids as each clutch has its own unique adaptive capability. EDS1 controls fluid pressure to clutch 1 which engages/disengages gears 1, 3, 5, 7, and R. EDS2 controls fluid pressure to clutch 2 which engages/disengages gears 2, 4, and 6

Hydraulic fluid pressure is regulated between the two clutches so when one is engaged the other is disengaged. During gear shifts, there is overlap between the two as shown in the lower plot in the drawing from ZF below. Both clutches can be disengaged at the same time when the vehicle is stopped or in neutral.




EDS3 (item 9 in the drawing above) – This solenoid controls an auxiliary fluid path for clutch cooling purposes.


EDS5 and EDS6 (items 4 and 5) regulate hydraulic pressure applied to the shift fork control rods within the gearbox. There are two separate shiftfork hydraulic circuits, one circuit to put the shift control rods in the retracted position, and another circuit to put them in the extended position. EDS6 appears to control fluid pressure to drive the shift rods to the retracted position, which applies to gears 1, 2, 4, and 7. EDS5 appears to control fluid pressure to drive them to the extended position, which applies to gears 3, 5, 6, and R. Failures that result in missing gear patterns like these can potentially be traced to these solenoids.

MV1 and MV2 (items 2 and 3) are binary control solenoids (on/off) that control shift fork actuation These solenoids work in tandem with EDS5 and EDS6 in selecting gear engagement. How their actuation maps to specific shift settings is unclear, but there is undoubtedly a truth table using MV1, MV2, EDS5, and EDS6 with combinations specific to each gear. I've not yet figured this pattern out, but am working on it.


Solenoid health can be evaluated via resistance measurements after disconnecting the solenoids from the Transmission Control Unit (TCU) circuit. This can be done by removing the transmission pan and disconnecting the harness, or more easily, by measuring resistance at the TCU harness. In the 997 the TCU is located in the rear of the vehicle interior beneath the door opening. The resistance can also be measured at the transmission connector, however it will be difficult to measure at this location with the transmission still in the vehicle. It is recommended that power to the vehicle be disconnected at the battery prior to disconnecting TCU connectors as this will minimize possible transient damage to the TCU.

Pinouts and characteristic resistances are shown below. Note that a normal resistance does not guarantee a solenoid is good, but an abnormal resistance almost certainly means there is a problem with either the solenoid or the harness to the solenoid (outside or inside the transmission).




There is a calibration procedure that is almost certainly required after replacing the valve body or a solenoid that will need a PIWIS and can be done by a good indy. Aside from this, a failed solenoid can be fixed for as cheap as $500 with a used valve body off Ebay and some DIY labor. It can be even cheaper if the fault code can help isolate which solenoid failed, and replace it alone. There’s nothing special about the solenoids in the PDK, the same parts are used on many ZF transmissions including those on BMWs, Audis, and Jaguars.



Sensors

The next three sections of the post detail the four sensor types in the transmission that provide data to the transmission control unit. Issues with any of these sensors will cause errors and may make the car undrivable as the control unit will think something is not functioning correctly.

Sensor types:

• Temperature sensor - one sensor, provides the control unit the clutch fluid temperatures
• Distance sensor (gearshift position) - four sensors in a single package, provides the control unit data on the gear position during and after shifts
• Speed sensor - two sensors in one package connected to the distance sensor, provides the control unit data on the input driveshaft speed
• Pressure sensor - two discreet sensors, provides the control unit with clutch fluid pressure into each clutch assembly

Failed Temperature Sensor

Another item that fails often is the clutch fluid temperature sensor. This is noted in numerous Porsche forum posts and a Porsche service bulletin (attached to this post). In this failure the ECU throws a fault claiming the PDK needs immediate service (“gearbox emergency operation” message) even though there is actually nothing wrong with the transmission. It also stores fault codes P0711 and P172D in the PDK control unit. In the 997.2 PDK this sensor is located above the valve body and accessible without removing the transmission.

Porsche provides a temperature sensor repair kit (PN 997.612.930.01) for only $35 that can be found here:

https://www.sunsetporscheparts.com/o...it-99761293001

This was a known defective part that was often replaced under warranty. The service bulletin claims you need a special crimp tool to install the new sensor and that only one crimp tool will be provided to each dealership (apparently it is a very special tool). (UPDATE: Kudos to psc85c who found you can get the magical crimp tool from Digikey for $233, about half the price of what Porsche lists. Link is below.) However, there is absolutely no reason the new sensor wires can’t be soldered rather than crimped (using high temp solder to be safe), sealed, and covered with chemical-resistant shrink tubing. The service bulletin goes on to make this completely ridiculous statement:



This is exactly the kind of nonsense that has misled many Porsche owners into thinking the PDK is disposable and they need to drop $20k for the failure of a thirty dollar part. There’s no reason the crimp can’t be repaired or even splice in a section of new wire if the connection is somehow fouled up. Yet some dealership grease monkey will solemnly state the transmission is toast because that is what the bulletin says. It’s completely ridiculous and frankly fraudulent.

Link to crimp tool from Digikey:
https://www.digikey.com/products/en?...2008-000&v=844

Here’s a picture of the new spliced in sensor wire prior to the applying the outer shrink tubing. This area is where the valve body would normally reside if it wasn’t dropped down for the repair.



As with the valve body, the temperature sensor health can be assessed via a resistance measurement at either the transmission "A" connector (difficult to access in the vehicle) or the TCU harness connector. Resistance varies with temperature so it's best to measure when the clutch fluid is at a known temperature (i.e. at room temp from being fully cooled off after use).




This is the temp sensor resistance versus temperature curve, an ambient temp of 20 deg C (68 F.) equates to about 950 Ohms.



So once again the PDK can be repaired for very little money ($40 sensor replacement) and the service bulletin doesn’t call for a calibration, probably since the valve body itself is not being replaced. You will almost certainly need a PIWIS to refill the transmission fluid correctly though.


Gear shift rod position sensor (distance sensor) and speed sensor failures
(6/26/21 Update: This section has been substantially updated as we’ve learned a great deal regarding PDK gearbox internals since this post was first put up 18 months ago. Thanks to Damien Law, Roberto, amet, Alexsey, Niklas Vemdal, T-design and many other for sharing what they’ve learned. Most of all, thanks for not believing Porsche’s nonsense and blazing a trail on this. The notion of a non-repairable transmission was obvious BS to many of us, thanks for proving it so.)

The gear position (distance) sensor is an electric sensor that measures the position of the control rods that engage gears within the gearbox. The purpose of this sensor is to verify things moved to the correct location when hydraulically commanded via the solenoids. These sensors are also used during PDK calibration as the transmission control unit correlates solenoid movement with gear movement. A faulty sensor will cause the transmission control unit to think the transmission is not shifting correctly.

Here’s a picture of the distance sensor (aluminum colored rectangle) with the attached speed sensor (yellow-orange) and the associated connector. The distance sensor is made by ZF and OEM parts are not available.




As is discussed at length in the comments on the original post, a dreaded PDK fault code of P1731, P1732, P1733, or P1734 almost certainly means the gear shift rod position (distance) sensor has failed rendering the transmission inoperable. Porsche refuses to make a replacement part available instead insisting that the entire transmission be replaced. I identified the part number for this unit and contacted ZF and was told that their contract with Porsche does not allow them to sell this part to the public. This is the typical corporate behavior I've come to expect from Porsche and VAG in general. Seriously, this is pretty fouled up and is indefensible.

If you google around you will find Chinese companies claiming to sell “reconditioned” PDK distance sensors. Every one of these vendors has been contacted and the part is out of stock. They may have had a few pulled from wrecked cars at one point, but they don’t have any now. You can try and pursue this and maybe you’ll get lucky but don’t get your hopes up as it’s very unlikely.

There is now another option from a company called T-Design. This is a brand new unit designed from scratch that replaces the failed factory distance sensor. Full disclosure, I know nothing about the performance or reliability of this replacement part other than anecdotal information, nor do I have any connection or any financial interest with the company. Additionally, the replacement part is not cheap, and you will need to find a cooperative and adventurous independent mechanic to do the work (many currently do not repair PDKs). It should be within the skills of experienced DIY-ers, but if you take your car for dealership oil changes it's probably not a job for you.

However, this is the only legitimate option (see update below) at this point IMO, short of replacing the PDK. Damien Law and Kuro Neko have posted their experience with T-design part on and report it works perfectly. Niklas Vemdal has also received the T-Design part for his failed PDK and hopefully he'll follow up soon with his experience. I'm looking forward to posting more success stories as we collect more information. With those caveats out of the way, here's the link to the part and a photo:

http://t-design9.com/porsche_PDK_dis...on_sensor.html




Note that you’ll need to splice the T-design replacement distance sensor into your existing harness as it does not come with a speed sensor or connector.

The yellowish device in the photos consists of two separate speed sensors. These measure the RPM of the two different input driveshafts (two clutches = two driveshafts). This mounts above and behind the gear selection sensor inside the gearbox section and provides data to the transmission control unit. There is no known drop-in replacement for the speed sensor but fortunately failures are uncommon. It probably can be repaired or perhaps even substituted as these types of automotive sensors are common and not complicated.

Unfortunately these sensors are located within the gearbox itself rather than the hydraulic section, and in order to replace it the gearbox must be separated. The picture below shows the location of the sensor within the 911’s PDK (tall black rectangular piece noted by the red arrow). You can see the black magnet appendages that are attached to the gear shift rods in the picture. As the rods are hydraulically moved back and forth the location of these magnets are sensed using a magnetic field sensor. These sensors then output a pulse width modulation signal proportional to the shift rod location.

The output of the sensor goes to a connector that is accessible outside the transmission (green arrow), the same connector shown in the photos above. I find it hilarious that the factory t-shooting guide states that gear oil leaks at this connector are caused by a damaged connector O-ring (a 50 cent part) and the remedy is to “replace PDK transmission”. Give me a freaking break.





Here’s a clearer cutaway shot showing the gear position sensor (black rectangle) and the shift rod appendages.







So is opening the PDK gearbox to replace this part feasible? It absolutely is and thanks to Damien Law and Roberto for documenting what was only conjecture when I first put up this post in Dec 2019. I’ve included a summary of Damien’s excellent photos and steps below.

For detailed info, please see Damien’s original post here:

https://rennlist.com/forums/997-foru...and-guide.html


To understand the PDK layout, take a look at the schematic below, in particular the bearings on the right-hand side. The driveshaft (top), mainshaft (middle), and pinion shaft (bottom) all terminate into bearings that are housed in the end case. When the end case is separated from the main PDK case the bearings remain fastened to the removed end case.





Here’s a shot of the separated PDK with the end case removed. Note how the three shafts are cantilevered out as they are supported by the remaining bearings in the PDK main case. This is an AWD transmission so the mainshaft (middle) has a splined end that protrudes through the end case for a coupling. 2WD PDKs don’t have this as the mainshaft ends at the end case bearing and does not protrude. The distance sensor and speed sensors are clearly seen at the top of this photo.






The case separation seam is noted by the red arrow in the cutaway drawing shown here. The end case would be unbolted and moved to the right in this example to gain access to the sensor.





After fluid has been drained the T-45 bolts attaching the end case need to be removed, there are additional bolts that continue below the PDK that can’t be see here. Note this is a 2WD PDK so there is a black cap where the mainshaft would protrude on the AWD PDK (lower cap). On a AWD you also need to remove the flanged coupling from the mainshaft prior to separating, it’s attached with a big nut.




In addition, this T-45 bolt on the side needs to be removed.




Next step is to remove the black end caps covering the driveshaft (2WD and AWD) and mainshaft (2WD only). You may be able to get these off without damaging them, but if not replacements are available from Porsche and they are not expensive ($5 each). The part number is 9G1.321.360.00 and you can get them from Sunset or other online dealerships, they are items #3 and #4 below but they have the same PN according to the Porsche Katalog.

https://www.sunsetporscheparts.com/o...se-9g132136000

(Update 1/18/22: I just checked the price on these and Porsche has jacked them up to $18 each, they were 5 bucks two years ago. Part of me wonders if it was in response to this post and it wouldn't surprise me if they stop selling them in the future. Make sure you have replacements in hand before you butcher these removing them. If anyone has a good method for removing them without damage please post in the comments.)






Once the caps are off there is a circlip/snap ring and a notched bearing lock nut (KM style) that need to be removed from the ends of the driveshaft and mainshaft (this should be obvious with the caps removed). This differs between the 2WD and AWD and isn't well documented so if anyone has additional info please post a comment.


After you are absolutely sure all the bolts are out it’s time to separate the case. This should be done with a dual puller (discussed below) as you need to simultaneously push on the driveshaft and mainshaft while pulling on the end case. Remember the bearings will stay in the end case so this step pulls the bearings off the shafts. It’s important not to get the end case crooked during the separation as that could put damaging stress on the bearings. It’s also important to not pry at the case seam as you don’t want to damage the gasket or stress the bearings. Replacement gaskets are not available as far as I can tell, so you’ll need to reuse it.


Here’s the puller Damien fabricated. A couple of standard auto parts store pullers could also be used by attaching them to steel barstock or an aluminum plate.








This is a nice graphic Damien made that shows how the puller works. Note how the bearings (shown in orange) pull off the shafts and are fixed to the housing. The short pinion shaft (not shown below) also pulls out of the housing, but it uses a roller bearing and is not a tight press fit. Note that the shafts have cavities at the end so you'll need to use a large thick washer or something similar over the end of the shaft to give the puller a place to seat.




Once the case is opened it’s a simple task to remove the distance sensor and speed sensor as they are only held in by a few bolts.






Installation is the reverse, and you should be able to pull the end case back on using the bolts around the seam. Use caution to ensure nothing is binding and the gap is closing uniformly. We don't know the correct bolt torque for certain but Damien reports he used 15 Nm with a small amount of medium loctite.

As an aside, another commenter reported that it’s possible to separate the PDK case with the transmission in the car on a Cayman. Presumably this applies to the Boxster also. Note that on these cars the PDK is oriented with the end case pointed toward the back of the car, and you can get full access by removing bumper cover and safety bumper. On the 911 the PDK is oriented with the end case pointed toward the front of the car, so there just isn’t the access available with the Cayman. It still may be possible but be careful as you don’t want to damage the bearings.




There are many other great photos in the comments section if anyone is contemplating this. Thanks to all who have contributed as my initial post was theoretical regarding this repair, based on what I thought could be done. In a little over a year you guys made it a reality. It truly was a team effort.

Beyond the sensors I’m working to compile a list of all potential mechanical wear items (bearings, seals) within the gearbox that may be replaceable. If you happen to open the gearbox, please post in the comments if you are able to obtain any other available part numbers or component dimensions that might be helpful.



Clutch pressure sensor failure

These are another two sensors that provide feedback to the transmission control unit regarding clutch engagement. They perform a similar function to the gear selection sensors in that they tell the control unit that the clutch is receiving fluid pressure when commanded by the solenoid. If one of these sensors fails the transmission control unit will think a clutch is not operating properly. Problems with these sensors usually show up as a P1706 fault code though there can be others.

These sensors reside behind the clutch and require transmission removal to replace them. Further, the clutch must also be removed (which isn’t hard if you know the trick). You can see the two sensors here where the clutch has been removed from a PDK transmission; these would normally be hidden behind the clutch. (For reference the gear in the upper right hand corner drives the PDK’s clutch fluid pump.)




Here’s the cutaway view below showing one of the sensors (red arrow) and the associated connector accessible on the outside of the transmission (green arrow). As with the gear shift sensor, you can likely perform some T-shooting via measurements at this connector. Note that this connector is the same one also used for valve body solenoid connections. This is the same round connector in the previously shown Porsche valve body drawings, the two small square connectors seen in that drawing are what attach to these clutch pressure sensors. On 991/981's PDKs with the locking differential option there is also a third pressure in this same area, the 997/987 PDKs don't have this third sensor.

The good news is that these sensors are replaceable by only removing the clutch; you do not need to open the gearbox. The harness unplugs from the sensors themselves allowing easy replacement.




The PN is 9G1.307.385.05 and it does appear in 997.2 PDK parts lists but the location is not shown in the parts diagrams. Further, it's also a ZF part like the valve body solenoids and the OEM PN is ZF 0501 326 481. (Update: Hat tip to Alexey who confirmed this is the right PN when he had his PDK removed. Thanks also to amet who confirmed the same sensor is used in 991.1 PDKs even though it's not listed in the parts diagram.)


I found this picture on a Polish website with a cost of $134 each.

https://maktrans.net/Dattchik-davlen...00-9G130738505

Sunset Porsche has the same PN for $144 (without a picture) so it’s also available domestically. This same sensor is a replaceable part used in the Panamera PDK so it should be available for the foreseeable future.

https://www.sunsetporscheparts.com/o...or-9g130738505

Once the transmission is out of the car the clutch can be removed to get access to the sensors using a homemade slide hammer as shown in the Champion Motorsport video below. They don’t explain how to reinstall the clutch but it can probably be pressed back on using a bolt and stacked flat washers. There may be a trick to aligning the clutch in the spline (I’ve never done it) so it’s probably a good idea to document the orientation of the clutch prior to removal.

https://www.youtube.com/watch?v=_nKmSVQdSr4

Believe it or not, that is it as far as the electronics inside the transmission. All of the smarts is located within the Transmission Control Unit which is remote from the transmission. When people say they had to have their PDK reflashed they are talking about the TCU, not the transmission itself.


Clutch failure

Last but not least is potential failure of the clutch itself. The good news is that these clutches have proven to be very robust and don’t fail often. The failures that do occur are usually on heavily built engines (e.g. 30% power over stock) with just too much torque for the clutch plates. At these high torques the clutches slip resulting in highly accelerated wear. There are replacement heavy-duty track clutches available for the PDK from Dodson Motorsports, but they are very expensive, on the order of $12k.

The clutch truly is a sealed unit and is not serviceable. There are different clutches for the Carreras (rated at 450 Nm) and the Turbo (rated at 700 Nm). I could not find any OEM clutch suppliers and only found one Chinese aftermarket supplier. Here’s a shot of what they advertise. They don’t list a price but say to contact them for more info.




This supplier only lists the lighter duty Carrera clutch as available and doesn’t have a listing for the Turbo clutch. Their website can be found here:

https://go4trans.com/porsche-pdk-7dt...l-clutch-assy/

As of June 2020 another Chinese aftermarket supplier now lists a remanufactured replacement clutch for $785. The link can be found here:

https://www.shenghaiautoparts.com/sh...ission-clutch/

I don’t think I would go this route unless I was really desperate as I can’t imagine the quality is anything close to OEM. Plus I’ve got a turbo so I’m SOL anyways. Fortunately these clutches don’t fail often so it’s unlikely I’ll need a new one. If it does fail it’s a good excuse to get the Dodson heavy-duty clutch and a monster engine build


Conclusion

To be blunt, I think Porsche’s “sealed” PDK transmission is a scam meant to separate us from our money. There are many relatively inexpensive, readily replaceable parts in this transmission that could be serviced by qualified shops and experienced DIY’ers. Failure of these parts likely makes up a large majority of PDK replacements. I think Porsche has deliberately withheld servicing information to create an aura of mystique around the transmission, to sucker us into thinking we have no choice but to drop $15K to $25k on a new transmission. I don’t see anything that makes this transmission so complicated or delicate that warrants their ridiculous policy. Frankly, it seems borderline illegal to me, violating consumer protection regulations.

To be fair Porsche dealerships do replace valve bodies on the PDK but there is little information on this available to the general public. I suspect there are also plenty of cases where a transmission replacement is performed by dealers when a valve body would have done the trick. On top of that, the Porsche list price for a valve body (which most dealers typically charge) is nearly $3k. Better than $15k but still absolutely crazy, particularly since a valve body "failure" is likely caused by a $50 solenoid.

As an experienced DIY’er, I will almost certainly forgo an extended warranty and attempt to repair the PDK myself if it fails prior to shelling out big bucks for a new transmission. The odds are really good the transmission can be repaired for less than 10% the cost of a replacement.

Note that pretty much every repair discussed here will require PIWIS service prior to being back on the road. Replacing the valve body needs a transmission calibration, as likely will installing a new clutch. (The PIWIS calibration procedure is described in detail in the first document linked at the bottom of the post. It's not difficult.) Any repair that removes the valve body (even if not replaced) will require a PIWIS for refilling the transmission. A Durametric can read the codes but it can’t perform the PDK commanding. So hopefully anyone affected is on good terms with a competent indy who can take care of this for a reasonable price. Also note that you’ll likely have to flatbed your car to the indy for the cal and/or fill procedure if you DIY the work.

BTW, it’s very likely a PIWIS is not required if one is simply draining the clutch fluid and not removing the valve body. The reasons are found at the link below, and the author explains in detail why that is the case and the tests he undertook using a PIWIS to demonstrate this. I find his rationale to be very compelling, and it squares with other information I’ve found in researching this transmission. This would also apply to the scheduled 60k mile clutch fluid replacement service.

https://www.planet-9.com/threads/diy...l-mode.237865/


Next steps
Compile transmission fault codes (readable with a Durametric) to cross reference against likely part failure and the repair process. Any help would be greatly appreciated!

Originally Posted by LLP

Hi everyone,

I am considering a 2009 Cayman S PDK with about 62k miles on the clock. The owner said that the car is suffering from a pressure sensor issue with its PDK and he managed to find an independent garage to fix it (so avoiding the usual Porsche bid to have you replace the entire PDK). What do you all think? Is this a common issue with PDKs and even if the sensor is replaced would there have been damage already done to the gearbox?