So, when the engine temp reaches it's normal (indicated) operating temp my transmission seems to go nuts. When moving off from standstill it feels like I'm trying to start in about 3rd - I have to give the accelerator a bootful and the car crawls until I'm doing about 10 km/h. All is normal until I stop again and the engine does that auto-shift into neutral.
If I crawl rather than stop there's no real problem, shifting from 1st right through to 6th is great.
Under the same conditions I can't reverse (I didn't try giving it a bootful as I was manoeuvring).

I have booked in for an ATF change which I need anyway - but any other thoughts?

Thanks MY11 SD4 SE Auto

Is this a sudden change or has it been slowly getting worse ?
Any evidence of loss of ATF from anywhere? Jules

It's a sudden change I think - hard to say as I only have a very short commute these days and the engine barely gets warm. I know, terrible.

No appearance of leaks anywhere. MY11 SD4 SE Auto

Have you had a diagnostic read on the TCM? It could be a control solenoid has failed, which should store a code in TCM. Hyundai Ioniq 5 Ultimate. The family car.
2009 Rimini Red SE TD4. Gone.
2006 Tonga Green i6 HSE. Gone.
Audi A5 convertible, my daily driver.
1972 Hillman Avenger GT, the project.

Nice diagnosis, will you be my mechanic?

P0744-68 torque converter clutch solenoid circuit intermttent.

Being discernible when the car has been on the road for a while, it performed ok for the mechanic because the trans hadn't been working. They kept it idling for a day but the fault didn't appear - obviously because the trans wasn't doing any work.
So it's a "sorry mate we couldn't find anything" despite the car telling them the problem.

Anyone know what the fix is? MY11 SD4 SE Auto