Hello, I'm having unusual issues with a MY2007 S80 equipped with a TF80SC, shifts absolutely perfect at high throttle/high rpm, no shudders (for the most part) and no slipping whatsoever, however the problems are as follows:
Upshifting 3rd to 4th in Drive (at low/mid rpm, ~40kmh shift point) kills acceleration, rpm drops then picks back up again - I can only imagine it erroneously applies the torque convertor clutch at low speed then disengages it, and later engages it properly at the intended speed (~50 kmh), if in manual mode waiting for the clutch to apply fully in 3rd gear then upshifting there's no issue, or just flogging it where the clutch doesn't really apply.
Downshifting from 3rd to 2nd creates a horrible jerking/shuddering, worse when cold, happens mostly when decelerating with medium/lower braking, does it when manually downshifting, again presumably the converter clutch is an issue considering how if it doesn't apply in the first place the downshift is unnoticeable.
I've had the car for about 4 months in which time it hasn't gotten worse or improved, previous owner said he changed the fluid AND did an adaptation, which leads to my question, is this potentially from a poor quality adaptation (like if the instructions weren't followed or was done in bad traffic) or some other software issue, I know of how picky these boxes can be with fluid and various valve body hijinks but it doesn't seem like it in this case, i can post the software ID of the TCM if needed or other information, since this one singular post is probably way too long already. Many thanks.
