Harsh shifts after new valve body. TCM required too?
05-07-2023, 05:45 AM
#1
Harsh shifts after new valve body. TCM required too?
I replaced the transmission valve body around 2,500 miles ago in my 2004 CTT which has around 200k miles on it. The car was experiencing all of the classic VB problems. I sourced a new VB and had it installed and the gearbox was almost completely cured other than having a harsh 2nd to 3rd shift on the odd occasion, but not enough to worry about.
Just recently however, shift quality has started to decline a little bit, and today I had something which I hadn't experienced since the old valve body was in the car - harsh downshifts from 5th to 4th where the car sort of 'dumps' itself into 4th at the wrong time and you feel like you're about to go through the windscreen.
The VB that originally came in 03 and 04 Turbo Cayenne's was superseded by a newer part number that started somewhere in 05, and that is the valve body my car now has with minor differences to the original. I asked Porsche if a new TCM is required to be installed at the same time as this updated VB but they said there was no requirement to do this. I have read other forums though where people have said a new TCM is required, or at least your original TCM needs to be updated or reprogrammed. If anyone can verify this or dispel any myths here that would be fantastic.
When my mechanic carried out the installation of the new VB I provided him with some Liqui Moly trans fluid for the refill, however I received more back from him than I was expecting. When I queried this he said that because the torque converter holds a fair bit of fluid that the refill amount was a fair bit less than the factory spec. Does this sound correct?
Just recently however, shift quality has started to decline a little bit, and today I had something which I hadn't experienced since the old valve body was in the car - harsh downshifts from 5th to 4th where the car sort of 'dumps' itself into 4th at the wrong time and you feel like you're about to go through the windscreen.
The VB that originally came in 03 and 04 Turbo Cayenne's was superseded by a newer part number that started somewhere in 05, and that is the valve body my car now has with minor differences to the original. I asked Porsche if a new TCM is required to be installed at the same time as this updated VB but they said there was no requirement to do this. I have read other forums though where people have said a new TCM is required, or at least your original TCM needs to be updated or reprogrammed. If anyone can verify this or dispel any myths here that would be fantastic.
When my mechanic carried out the installation of the new VB I provided him with some Liqui Moly trans fluid for the refill, however I received more back from him than I was expecting. When I queried this he said that because the torque converter holds a fair bit of fluid that the refill amount was a fair bit less than the factory spec. Does this sound correct?
05-08-2023, 02:47 AM
#2
Pro
When the valve body was replaced, were the adaptations cleared in the transmission? If not, that's the first thing I would do. Your symptoms of a harsh 5-4 downshift and 2-3 upshift sounds like the new valve body may be having issues too. Do you have any kind of warranty on it?
Regarding the TCM, they cannot be reprogrammed as the programming is hard-coded into them. They cannot be software flashed. There was a revised TCM that was introduced into production vehicles in July 2004 to fix the harsh 1-2 shifting when cold. I don't know if there was another TCM revision after this when the valve body part number was changed. I have attached the TSB from Porsche with the part numbers. Depending on your VIN, and your current TCM version, your DME may need a software update in order to play nice with the updated TCM. I have also attached the procedure for installing a new TCM.
Yes, the torque converter holds a good amount of fluid. Typically, a simple drain and refill of an auto transmission only gets about 1/3 of the fluid out. However, I would check the fluid level using the official procedure, as low (or high) fluid could also cause the issues you are experiencing. Also check the wiring harnesses at the transmission and the TCM to make sure they are dry, as trans fluid can find their way into those connectors.
Regarding the TCM, they cannot be reprogrammed as the programming is hard-coded into them. They cannot be software flashed. There was a revised TCM that was introduced into production vehicles in July 2004 to fix the harsh 1-2 shifting when cold. I don't know if there was another TCM revision after this when the valve body part number was changed. I have attached the TSB from Porsche with the part numbers. Depending on your VIN, and your current TCM version, your DME may need a software update in order to play nice with the updated TCM. I have also attached the procedure for installing a new TCM.
Yes, the torque converter holds a good amount of fluid. Typically, a simple drain and refill of an auto transmission only gets about 1/3 of the fluid out. However, I would check the fluid level using the official procedure, as low (or high) fluid could also cause the issues you are experiencing. Also check the wiring harnesses at the transmission and the TCM to make sure they are dry, as trans fluid can find their way into those connectors.
Last edited by Malibu955; 05-08-2023 at 02:48 AM.
05-09-2023, 04:40 AM
#3
When the valve body was replaced, were the adaptations cleared in the transmission? If not, that's the first thing I would do. Your symptoms of a harsh 5-4 downshift and 2-3 upshift sounds like the new valve body may be having issues too. Do you have any kind of warranty on it?
Regarding the TCM, they cannot be reprogrammed as the programming is hard-coded into them. They cannot be software flashed. There was a revised TCM that was introduced into production vehicles in July 2004 to fix the harsh 1-2 shifting when cold. I don't know if there was another TCM revision after this when the valve body part number was changed. I have attached the TSB from Porsche with the part numbers. Depending on your VIN, and your current TCM version, your DME may need a software update in order to play nice with the updated TCM. I have also attached the procedure for installing a new TCM.
Yes, the torque converter holds a good amount of fluid. Typically, a simple drain and refill of an auto transmission only gets about 1/3 of the fluid out. However, I would check the fluid level using the official procedure, as low (or high) fluid could also cause the issues you are experiencing. Also check the wiring harnesses at the transmission and the TCM to make sure they are dry, as trans fluid can find their way into those connectors.
Regarding the TCM, they cannot be reprogrammed as the programming is hard-coded into them. They cannot be software flashed. There was a revised TCM that was introduced into production vehicles in July 2004 to fix the harsh 1-2 shifting when cold. I don't know if there was another TCM revision after this when the valve body part number was changed. I have attached the TSB from Porsche with the part numbers. Depending on your VIN, and your current TCM version, your DME may need a software update in order to play nice with the updated TCM. I have also attached the procedure for installing a new TCM.
Yes, the torque converter holds a good amount of fluid. Typically, a simple drain and refill of an auto transmission only gets about 1/3 of the fluid out. However, I would check the fluid level using the official procedure, as low (or high) fluid could also cause the issues you are experiencing. Also check the wiring harnesses at the transmission and the TCM to make sure they are dry, as trans fluid can find their way into those connectors.
Adaptations were cleared but maybe worth doing again to be thorough.
I bought the new VB a while ago now and typically these things only have 30 days warranty on them so I'm probably out of luck. The company who supplied it is reputable though (LBM auto parts in Sweden) so it's not like I bought a dodgy Chinese knockoff or something.
Unsure what I should do regarding the TCM. If Porsche say there's no need to upgrade I believe them so that probably isn't the issue. I will check the wiring harness though and make sure it's dry.
As for the fluid level, is it worth doing a flush to get more fluid out of the trans or is that asking for trouble on an old gearbox like this? Perhaps with so much old fluid left in the torque converter it has clogged up the VB again hence the returned harsh shifts?
05-09-2023, 04:56 AM
#4
Pro
Don't flush the trans. Do a 3X drain and refill:
Drain and refill the fluid. Drive for 200 - 300 miles. Repeat two more times. That should exchange about 90% of the old fluid with new.
At your mileage, if the transmission was working flawlessly, and you didn't have any records of the fluid being changed, I'd leave it alone. However, since you are having issues, I would change the fluid as described. First though, check the level.
Drain and refill the fluid. Drive for 200 - 300 miles. Repeat two more times. That should exchange about 90% of the old fluid with new.
At your mileage, if the transmission was working flawlessly, and you didn't have any records of the fluid being changed, I'd leave it alone. However, since you are having issues, I would change the fluid as described. First though, check the level.
05-11-2023, 03:02 AM
#5
Don't flush the trans. Do a 3X drain and refill:
Drain and refill the fluid. Drive for 200 - 300 miles. Repeat two more times. That should exchange about 90% of the old fluid with new.
At your mileage, if the transmission was working flawlessly, and you didn't have any records of the fluid being changed, I'd leave it alone. However, since you are having issues, I would change the fluid as described. First thought,k th check the level.
Drain and refill the fluid. Drive for 200 - 300 miles. Repeat two more times. That should exchange about 90% of the old fluid with new.
At your mileage, if the transmission was working flawlessly, and you didn't have any records of the fluid being changed, I'd leave it alone. However, since you are having issues, I would change the fluid as described. First thought,k th check the level.
What makes it tricky to diagnose is that replacing the valve body has predominantly solved the problems it was having which were bad enough to throw it into limp mode as the shifts were very violent.
Now it works well for the most part but these occasional harsh shifts are a bit concerning.
Do you think it potentially suffered some damage during the period where the old valve body was malfunctioning and the random harsh shifts are a result of that?
05-14-2023, 05:29 PM
#7
Rennlist Member
you can check your trans connections also. if they are wet with fluid, as someone said above, this can cause issues. changing out the harness is not hard, just messy. Effectively a valve body replacement. If the connectors on the outside are bad, you'll have to renew them. One is a jetta headlight connector and the other is a passat fan connector. I did mine when changing out the internal harness due to leaks from inside to outside. If the fluid is leaking, it can creep up the inside of the wires and work its way into your TCM. Bad thing that is. You don't want that. Also, if by chance, your valve body went bad, I have an 05 valve body that I bought and didn't use because it didn't fit my 06 ctts.
