TCM linked to valve body issues?
09-08-2023, 09:48 PM
#1
TCM linked to valve body issues?
I've done quite a lot of reading of valve body threads in this forum and others too, however one thing I've been unable to ascertain is whether or not 1) a new TCM is required when updating to the newer valve body (95532503900 - turbo part number) which supersedes the old one. 2) If the old TCM's can be 'fixed' with a Porsche software update (FCP Euro touched on this in their comprehensive Cayenne transmission video)
3) TCM's need coding to work with different valve bodies when undertaking a replacement (again, FCP touched on this but not in great detail, so I have no idea what constitutes a need for coding and what doesn't).
It would be great to understand this in more detail as I feel this is a topic that's somewhat shrouded in mystery, at least for those of us who aren't actual Porsche techs.
My reason for wanting to understand this better is that I replaced the original valve body in my 04 CTT last year, and while the car is actually driveable now and behaves well for the most part, it does still have 'bang' shifts on occasion and just generally below-par shift quality with clunks, etc. While I'm very much aware this could just be the result of a dodgy replacement valve body, I'm always left wondering if maybe the TCM is also somehow responsible, especially because the shifts aren't consistently bad - it feels very much like a control problem and not something caused by actual gearbox hardware.
3) TCM's need coding to work with different valve bodies when undertaking a replacement (again, FCP touched on this but not in great detail, so I have no idea what constitutes a need for coding and what doesn't).
It would be great to understand this in more detail as I feel this is a topic that's somewhat shrouded in mystery, at least for those of us who aren't actual Porsche techs.
My reason for wanting to understand this better is that I replaced the original valve body in my 04 CTT last year, and while the car is actually driveable now and behaves well for the most part, it does still have 'bang' shifts on occasion and just generally below-par shift quality with clunks, etc. While I'm very much aware this could just be the result of a dodgy replacement valve body, I'm always left wondering if maybe the TCM is also somehow responsible, especially because the shifts aren't consistently bad - it feels very much like a control problem and not something caused by actual gearbox hardware.
Last edited by tassieporsche; 09-08-2023 at 09:50 PM.
09-09-2023, 07:56 AM
#2
Instructor
Sorry, I cannot speak to the question but as an answer to the clunky shifts I can say that you should get your hands on a food scan tool and reset the shift adapts. Over time the TCM “learned” to adjust shifts to individual driving style and compensate for normal transmission wear. Reset those and in a very short time your shift quality will improve.
