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Discussion Starter · #1 · (Edited)
This section covers basics of PDK servicing as well as a full tear down of the transmission and explanation of transmission components.

981 Transmission mounts




981 Transmission (PDK) removal




981 PDK oil change information




Oil pan and filter




Clutch pack

 

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Hi, I have a 2013 Boxster when coming to a stop the transmission will stick in a gear. Usually when getting of the freeway it sticks in 4th gear but I've had it stick in 7th gear. Last week, when driving it home from the dealer, on surface streets, it stuck in 2nd gear. The dealer tells me there is a a failure on the Internal Transmission Sensors (fork position sensor) (I can send you the info in the report) and says the transmission needs to be replace ($18k). The dealer hasn't ruled out the possibility of replacing the PDK control unit ($2.1k).

I've called all the local independent Porsche mechanics and one has seen (3) 981 Boxsters with the same issue. He sent them to a dealer for a transmission replacement. There also appears to be a number of postings for 981's with this issue. From the videos you have posted, it appears you are very familiar with the PDK. Have you seen this problem? Is it repairable without purchasing a new transmission? Is this an prodominat issue with the transmission that warrants a recall?

I'd appreciate any advice you can provide.
 

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I'm not @jjrichar, but a comment or two:

There is a company that makes replacement position sensors for the 987 PDK transmission. They make the replacement sensor because some of the originals had issues. I don't know if they have a replacement sensor for the 981 PDK transmissions, but AFAIK - these transmissions are almost identical. A dealer won't even attempt to fix a PDK transmission. There is at least one company here in the US that now offers some services on internal PDK components.

You might look at: Position Sensor PDK Porsche and 7 Speed PDK parts
Also: Displacement Sensor Install (gear position, distance sensor) for 911, Boxster, Cayman, 997, 991, 981, 987 - which has sensors that work with the 987 and 981, and a link to an article on how to install it. Perhaps if you find a good transmission shop they might consider doing it.

And when you have a moment, please visit New Member Introductions and introduce yourself and your Porsche. Photos are always welcome!
 

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Discussion Starter · #8 · (Edited)
I'd appreciate any advice you can provide.
Whilst I'm tearing down a transmission, I'm not an expert in diagnosis. I've attached a bunch of Porsche PDK documents to the first post above that could help.

From what I've seen elsewhere, the distance sensor is the most likely sensor to fail in the transmission. Hence why there are aftermarket options as linked by Deilenberger above.

Getting a PIWIS or equivalent onto the car to get the fault codes is essential to diagnose where the problem is. If you have one or more codes 1731 through 1738 then it's the distance sensor. Attach the report you have to a post in this thread.

To be honest those symptoms seem a bit weird. Gears 7, 2 and 4 are all on different shift rods, so I don't think it's the distance sensor. Normally it's just one of the four individual distance sensors that fails.
 

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Discussion Starter · #9 ·
There is a company that makes replacement position sensors for the 987 PDK transmission. They make the replacement sensor because some of the originals had issues. I don't know if they have a replacement sensor for the 981 PDK transmissions, but AFAIK - these transmissions are almost identical. A dealer won't even attempt to fix a PDK transmission. There is at least one company here in the US that now offers some services on internal PDK components.
Great input. Much appreciated.

I've seen the T design sensor before and it clearly is a good replacement option. I'm not sure if the other one is a rebranded version of it. Unfortunately these are pretty expensive. To be expected as this is really the only option available. From what I understand it's the same sensor in all of the 7 speed 911 and 981 transmissions.

Something I'm working on at the moment is trying to gather as much information about the distance sensor as possible to try and work out exactly how to replicate it. My end game is to find out how to fix a distance sensor. I plan to post a video soon with all the information I have to hopefully have some experts nut it out.

I've got the serviceable distance sensor from the tear down, as well as a serviceable car and PIWIS to see what the car expects and also what responses an external sensor gives from the car. The common input for all 4 sensors is 5V with a common ground. The output is a voltage relative to the common ground that shows the distance from the sensor.

I was using 3 x AA batteries (4.5V), and the response ranged from 4.2V (no magnet close) to 0.4V when the magnet was right on top of the sensor. From what I understand the OEM sensor is very old school and is an inductive coil. The aftermarket versions are solid state hall sensors.

The response from the TCM is a range relative to the center position of up to 12.7mm, so a total range of about 25mm. The movement of a shift fork to select a gear is about 10mm.

To me it seems to be a case of working out the spec of the hall sensor and just install. The sensor itself has an aluminium shell with the electronics installed, and then it's filled with epoxy. I can't think it would be too hard to grind out the epoxy and then install new sensors/wiring and refill with epoxy. If the sensors are easily obtainable and not expensive this might be a good alternative to paying US$2000 for a new sensor.
 

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Discussion Starter · #11 ·
That looks like a distance sensor problem. First thing I'd do though because it's intermittent is get under the car and disconnect/reconnect the rear transmission plug a few times to ensure it's not just a connectivity problem. I've had this happen a number of times on other transmissions (same plug). You just need to get the tab on the plug and move it up and down a few times. This will move the contacts over each other. If you can see oil around the plug I'd be fully disconnecting and cleaning both parts with contact cleaner. It might not be this but it's something you can at least check prior to pulling the gearbox apart.
 
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