Shudder in 3rd 1800-2200rpm

[MikkiJayne]

Hi all,

At long last my S8 is all back together and almost all behaving properly, apart from a weird shudder in 3rd gear when warm / hot. It only happens at light throttle, going up a hill, from 1800-2200rpm. A bit of throttle will clear it, backing off won't, and it doesn't do it in S because it will be in 2nd in the same places where it would be picking 3rd in D. It does do it in tiptronic under the same conditions. It doesn't do it from cold - it needs to be driven for about half an hour, although I haven't spotted the temperature it starts at yet. >45* I think.

Its quite a vigorous shudder - much more harsh than a misfire. No codes whatsoever- ecu, tcu and abs are all clear. It will throw the 11119 missing gear signal code in tiptronic, but that seems quite common. Other than the shudder it drives just fine, shifts smoothly (no thump), kicks down fine, pulls away fine. I've had a co-pilot watching vcds and there's no observable change in rpm, engine load, engine request, torque converter clutch, F125, or gear selection.

The gearbox has had the problem bearing and o-ring changed (although they were fine when I took it to bits), and the clutch packs looked fine. It took the full 9 litres of fluid when I refilled it at 35*. The tcu has been encouraged to re-do its basic settings since it has been disconnected for a while.

Any ideas please? I'm completely stumped and can't even find any reports of similar symptoms on t'interweb