Transmission limp mode after long ride in hot weather

[vratnik]

Occassionally when driving at high speeds on highways (150+ km/h) for prolonged time (several hours), during temporary high rpm events like overtaking or a hill, I can hear a whine sound at about 4000 rpm. Then the car seems to lose power, slows down, doesn't accelerate just keep speed, or decelerate if going up hill. No error messages or warning lights. Gas pedal on the floor, RPM maxes at 2000 and refuses to go above. This happens only in summer. I can move the shifter to "fake manual", trying to use paddles does nothing, "gear" is stuck at nr. 6. After shifting it back to automatic,, it will revert to normal operation but only for a very short time. Just enough to accelerate, than again switches to limp and just so-so keeps the speed on a flat road. Eventually it decelerates to 100 km/h or even less if the road goes upwards. I have to stop it on the near resting place and have it cool down a bit. Then it drives ok again.
From what I read on the internet it seems there is too much oil in my transmission which overheats it and forms a foam.
The dipstick shows about 5mm above highest level in the heated state. in cool state, it is also too high, somewhere in the H area.

I'll end this with a dumb question: Should I pump out some of this oil through the dipstick tube?
Another thing: The transmission got overhauled 2 years ago. viewtopic.php?f=12&t=4537&p=54991#p54991
Any other ideas?

[old tech]

If the transmission has been rebuilt or exchanged, there is a possibility of getting some different parts in there. It would be important that the right combination of transmission pan, pick up screen, and dipstick are all supposed to be together. There are two different depths of pan and, three different dip sticks and possibility more than a few different pick up screens. Showing a picture of your transmission pan and the total length of your dipstick. We can see whether we at least have those two items matched and then confirm that the level could be set correctly. Does the fluid still look really nice? If you had access to a scan tool, you could watch the live data and see what the temperature of the fluid is right at the valve body. Another thing that would be nice to check is all of the computers on the car before shutting the car off.


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[vratnik]

Thank you for your valued reply. Had it checked by the workshop where they had rebuilt the transmission. They didn't see any problem. Oil looks ok. They also told I should measure oil with engine on. Only then it shows correct level. Next thing, because they can't simulate long drive, they will borrow me their computer on my next long trip. They will explain me how to measure etc, it will measure various temperatures and other data of the transmission. I will update in a month.

[Woodie]

Occassionally when driving at high speeds on highways (150+ km/h) for prolonged time (several hours),

I've been driving 50 years and I can't even imagine this possibility.