My car runs fine before the ATF change, I changed the ATF just as a precautionary measurement because I want to keep my Phaeton for a long time, after the ATF change, the car was fine when I drove 300 KMs back home, (that was back in October), but recently I have noticed something strange with my transmission, it doesn't do that all the time, just when the temp is below freezing point (especially below minus ten, but in Canada, we can get -20 or even -30 easily): the transmission seems jerks between 3 to 4 and 4 to 5, and sometime you can feel a moment of power loss when the gear shifts to 5th gear. and when the car goes down hill, the RPM jumps up and down when the gear is not actually shifting. the symptom seems getting better when the transmission completely warms up.
At first I thought it is because the dealer didn't upgrade the TCM and ECM as I read post on the TOC, the transmission software will need to be upgraded when the fluid was changed, the ATF dealer put into my transmission is G060162A2, I have contacted several other VW dealers and ZF, confirmed that is the correct part number for my Phaeton, but got mixed results on the TCM upgrade, all the VW dealers I talked to said the TCM doesn't need to be upgraded in my case, and it is when you update the TCM, fluid needs to be changed and not the other way around, but the email I received from ZF said the TCM needs to be updated, otherwise the clutch could be burned after a longer time.
I have been doing research online, and seems the jumping RPMs is related to the torque convertor, or the trans filter wasn't installed correctly. I talked to the service manager of the dealer which performed the work on my car, he said from his experience, sometimes a transmission with such high mileage, if you changed the ATF, it might have some problems, as the detergent in the new ATF will wash out the residue in the old transmission which the transmission already relies on to maintain proper seal, it might settle down after some time. I also performed a Vag-Com scan on my car, but shows no fault code found on transmission.
I am getting mixed information and really frustrated right not, now I feel I should believe "if it is not broken, don't fix it", I want to take care of my transmission by changing the ATF, but now I end up start to have problems, what shall I do now? Is it just because the new ATF is very sensitive to low temperature? Or is there something wrong with my torque convertor or is it because the dealer didn't do the job right?