Just logged in and saw your reply mcs, thanks!
A actually did what you suggested. When I realized the gearbox is a common ZF 6HP26 was wide open
So much to read on BMW/jaguar pages.
I came to the decision to start just changing the ATF fluid. Couldn't see any notices in the service booklet about it ever being changed event though that doesn't guarantee anything. Reason for the change was that better to start off replacing some of the potentially really old fluid to see any improvements before doing more work. Agree that just pulling the mechatronic unit and replace the seals wouldn't be that hard. Save that for later.
Reading Jaguar forums I noticed a method that used the internal ATF pump to pump out fluid via the cooling outlet and then just doing refilling through the return line. That sounded like a good idea to replace more than the accessible fluid. So that is what I did...
First inspection indicates some kind of leak. Can't really say where it's coming from so it is hard to say if it even is ATF fluid or engine oil. Pretty messy around the sensor at the bottom but didn't bother. Need to do my homework on what it is before.
Pulled the ATF cooler, started the engine to find which is the exit/return lines. The front one is return, the ATF fluid comes out of the rear one. Fine.
Drained the transmission, pulled the pan and filter. Let it drain during the night, new filter, pan gasket and then assemble. Made a simple adapter to connect hoses in place of the cooler. I printed the green plastic thingies on my 3D printer. The plywood piece has holes for two M6 screws and the hose connectors. Center measurements for screw-hose-hose-screw are 0-36-70-128 mm.
idea was, according to my Jaguar fellows that the return line dumps into the pan. The pump then sucks up new ATF fluid through the filter and pushes out old through the cooling exit. In theory, one would see fresh ATF fluid coming out but that didn't happen. At least the fluid spit out at the end was less black than what I first drained.
I first pressure-filled about 6 liters of fluid to replace what I drained during the night. Then started engine to drain one liter, filled up with a new liter and so on until I realized I had put 12 liters into the whole thing.
My plan was to just fill up the transmission with too much fluid and rain it off during the level check. Unfortunately I didn't have enough fluid so when doing the level check it was too low. I had then mounted the cooler. Had to wait a day to get more fluid and fill it up the normal way.
In the end I think the transmission was about 500ml low on fluid and the fluid seemed to be in really bad shape. Deep black. Magnets looked good though, just some minor metal slush on them.
So how did it work out then? Fine. I haven't done the adaptation reset yet, just took it for a test drive of about 20km in different conditions. Shifts are smooth and happens when expected, gears are locked and so on. Still assume I need to reset the adaptations and do the adaptation runs on an empty road?
Lessons learned:
- Buy more ATF fluid than you think you need when you order it from a cheap reseller to avoid having to buy additional at a steeep price...
- The flush method using the cooling lines may not really work that well on the Audi version of the 6HP.
- I will need to redo this sometime in the future due to the potential leak.
I also learned a lot about the ZF gearboxes and gained more hands-on experience. Nice.
If I encounter more new problems I will gear up with new sealings to the mechatronic unit and replace them when having things apart.