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The temp sensor is a thermocouple whose resistance varies in proportion to the temperature change. I think Porsche is concerned that a poor quality crimp could introduce resistance in series with the thermocouple that corrupts the measurements. Since the connector is immersed in clutch oil, it will also be exposed to a large temperature range that could cause a change in resistance if there is a poor quality connection.
That's why I suggested using a high-quality sealed solder connection. However any method that is low resistance along with being heat and time stable should work. It also needs to be sealed as you don't want to deal with the possible corrosive effects of clutch fluid. The shrink tubing Porsche supplies with the kit has epoxy inside that melts and encapsulates the connection when shrinking.
The temp sensor is a thermocouple whose resistance varies in proportion to the temperature change. I think Porsche is concerned that a poor quality crimp could introduce resistance in series with the thermocouple that corrupts the measurements. Since the connector is immersed in clutch oil, it will also be exposed to a large temperature range that could cause a change in resistance if there is a poor quality connection.
That's why I suggested using a high-quality sealed solder connection. However any method that is low resistance along with being heat and time stable should work. It also needs to be sealed as you don't want to deal with the possible corrosive effects of clutch fluid. The shrink tubing Porsche supplies with the kit has epoxy inside that melts and encapsulates the connection when shrinking.
Makes sense. Probably the same reason they are concerned about the wire length itself. I wonder if there is a tension load on the wire that needs the mechanical connection of a crimp over solder. I suspect they opted for a mechanical connection because it's easier for the average mechanic than a quality solder connection would be. Who knows.
There is a SolderSleeve that is immersion-proof that might do the trick, although I'd want to look up what the NAS1744 standard says to see how immersion-proof it really is.
I've added a bunch of additional information about the functions of the individual solenoids that should be helpful in troubleshooting. A replacement solenoid costs less than 5% that of a new valve body so hopefully this information can save someone some money.
Just seeing this thread. Way beyond my capabilities but just knowing far better how the thing works and can be maintained helps a lot. Thanks for all your research !!
Those look similar to the TE/Raychem SolderSleeves. The only issue I have is whether the heat-shrink part is compatible with the gearbox oils. I just haven't looked to see.
If you want expensive crimp tools, take a look at the certified ones for aerospace use; the Porsche one is ordinary commercial grade. :-)
My recollection is the Raychem heat shrink material is heavily cross-linked (via irradiation during the mfg process) , that are effectively very high molecular weight polymers, which have much better oil compatibility than similar low molecular weight polymers. So yes, they should be good.
PV997 Thank you so much for doing all this amazing work!!!
Here is my small contribution and maybe everyone else who had a PDK replaced can chime in.
I'm on my 3rd PDK, meaning my two prior PDK failed on me and got replaced by Porsche
Here are the error codes I pulled with the Durametric and my symptoms
PDK #1:
Symptom: transmission is stuck in 2nd gear
Durametric codes:
1706: Sensor supply voltage 5V too low (not 100% sure if that's a PDK error code)
1731: Shift rod 1 displacement sensors
PDK #2:
Symptom: transmission stuck in Neutral
Durametric code:
1731: Shift rod 1 displacement sensors
Thanks Hatzenbach, that is great info and hopefully we;ll get more of these reports to help sort out what exactly is going on.
Both of your incidents indicate a failure with the gear shift selection sensor (also called a distance sensor) that I discuss in the post. This sensor measures the position of the shift rods that control the shift forks when switching gears. The P1731 failure is that the sensor is providing a value outside the valid range which likely means the sensor has gone bad (as opposed to the shift rod being controlled improperly by a bad solenoid).
I think I remember reading reading your failures happened when tracking the car and there were suspicions it was heat related. This supports a theory I've been kicking around regarding failure of this sensor. This sensor is in the gear case, not the hydraulic section, and it's immersed to an extent in gear oil. In the 997, the PDK has a clutch fluid cooler but not a gear oil cooler. Porsche added a gear oil cooler to the PDK in the 991's and I wonder if part of the reason may have been due to failures of this sensor. Electrical components usually don't like heat and high temp gear oil could have decreased the sensor's reliability. PDK replacement is often attributed to failure of this sensor in comments I've found online.
As an aside the symptoms you noted (stuck in one gear) where probably not from the failure itself but from the transmission control unit's reaction to the fault. When the TCU sees these types of faults it disables all sorts of functions within the transmission. I suppose this is done to protect the transmission but it makes it seem like many things have broken when they really haven't. There's probably good reason for this but it seems a little shady to me as folks think their transmission is completely hosed since everything seems to have gone wrong when the actual impact of the fault itself is much less.
Here's the effects of the P1731 fault, the first three are TCU induced and result in it being stuck in one gear:
Last edited by PV997; 01-03-2020 at 11:02 PM.
Reason: typo
Thanks great info. The obvious question is now if it’s possible to add a gear oil cooler aftermarket.
There is a pricey aftermarket gear oil electric pump/cooler available from Bilt Racing at the link below. The kit is intended for Caymans as they have issues with oil starvation in the differential. (Since their PDK is rotated with the differential in the front, it get starved under heavy acceleration as gear oil moves to the back.) I can't see why it wouldn't work for a 997 too. There may be cheaper alternatives, this is one I happened to come across when looking in it.
There is a pricey aftermarket gear oil electric pump/cooler available from Bilt Racing at the link below. The kit is intended for Caymans as they have issues with oil starvation in the differential. (Since their PDK is rotated with the differential in the front, it get starved under heavy acceleration as gear oil moves to the back.) I can't see why it wouldn't work for a 997 too. There may be cheaper alternatives, this is one I happened to come across when looking in it.
I can't envision any way to fit the factory 991 PDK cooler to a 997. I'm not exactly sure where the pump is but I think it's internal to the gearbox.
Great info ... all of this leads me to never want to track my 997.2 pdk unless it is a couple of easy sessions.
A reasonably priced 997 PDK cooler that has a good history of doing the job of preventing heat related issues seems like it could be very popular.
Great info ... all of this leads me to never want to track my 997.2 pdk unless it is a couple of easy sessions.
A reasonably priced 997 PDK cooler that has a good history of doing the job of preventing heat related issues seems like it could be very popular.
It's just a theory at this point and as usual, Porsche isn't offering much information. The 991 technical training material speaks of adding the gear oil cooler for the differential, but that doesn't make much sense as the differential is in the back in the 911 (unlike the Cayman) so under heavy acceleration it should have plenty of lubrication. Maybe Porsche added it for the Cayman and left it in for the 991 too.
The gearshift sensor thing makes sense though, and it's interesting that both of Hatzenbach's failures were on shift rod 1 (there are four). Maybe that's the one in the hottest location? I'll see if I can figure out which of the rods is #1. Porsche has not made it easy to sort this stuff out.
not trying to take over your thread, but I also found this one: https://www.teambgb.com/BGB-Motorspo...-p/bgb_tck.htm I find it interesting that all of the solutions offered are for Caymans
It looks to me that it actually shouldn't be that hard:
There must be a hole to fill in gear oil and there must be one to drain it.
So all you have to do is to
add pipes to both holes,
add an off the shelf oil cooler and
and electric pump,
route everything to the front and put the oil cooler in front of the 3rd radiator
not trying to take over your thread, but I also found this one: https://www.teambgb.com/BGB-Motorspo...-p/bgb_tck.htm I find it interesting that all of the solutions offered are for Caymans
It looks to me that it actually shouldn't be that hard:
There must be a hole to fill in gear oil and there must be one to drain it.
So all you have to do is to
add pipes to both holes,
add an off the shelf oil cooler and
and electric pump,
route everything to the front and put the oil cooler in front of the 3rd radiator
Not taking over the thread at all, any ideas that help people save $20k on a "failed" PDK are welcome. The pictures I've seen on Caymans involve drilling holes in the PDK case for the hoses but using the drain and fill holes is a great idea. For Caymans the returned (cooled) oil is shot right onto the differential which is pretty far from the fill plug. But for 997's you might not need that since the differential should not be a problem due to its location. I think that the kits are marketed toward Caymans/Boxsters is due to their unique differential orientation since they're mid-engined.
Having an air/oil cooler up at the front would be best but you might be able to get away with a water/oil cooler like is done in the 991. This is what the clutch fluid uses and you could probably scab off the coolant lines feeding it. You still need the electric pump but don't need to run gear oil lines to the front of the car.
Here's the 991 gear oil cooler, interestingly it's used in both the AT and MT (the 991 MT is based on the same gearbox as the PDK AT). It's attached to the side of the gearbox.
...I'll be adding new info to the post as it becomes available...
If ever there is an annual Porsche-Savior prize (I suggest we call it the 'Peter Schutz' prize), I'm nominating your good self
Anyway...
There are two 997.2 hardcopy publications out there that have PDK related information. I'd be amazed if they add anything significant beyond what you've already added, so the following is just an FYI...
The first is a manual designed for US Porsche Sales Staff, to help pitch the 997.2. It has a 25-page section on the PDK. Here's a random screen shot from that section:
The next one was meant to be a technical introduction of the 997.2 to PCNA. In no way is it at the level of the factory manuals. But its 43-page section on the PDK might yield a few insights. Ditto on the snapshot...
Both of the above popup on eBay on a fairly regular basis for less than $50 per copy (I got both of mine for less than $25 a copy).
There are two 997.2 hardcopy publications out there that have PDK related information. I'd be amazed if they add anything significant beyond what you've already added, so the following is just an FYI...
The first is a manual designed for US Porsche Sales Staff, to help pitch the 997.2. It has a 25-page section on the PDK. Here's a random screen shot from that section:
Hey Karl - Thanks for posting this, people are sending me all sorts of stuff that has been helpful in unraveling this.
I have the second document so I'm good there. I don't have the first document but it might not be that helpful if it's just marketing fluff. Please let me know if there is any info in it specifically on the hydraulic circuits (hydraulic schematic, description of solenoid functions, etc.). I've been able to piece together most of it but there's some conflicting info and it would be good to have more sources.
12-16-2019, 11:12 PM
