I have a problem that I would like to know if anyone else has experienced this. Whenever I drive up a hill for any EXTENDED period of time, where the transmission is using 4th gear to pull me up the hill, after the crest of the hill, my car will stick in 4th gear. My manumatic mode disables itself and wont allow me to change the gear manually. Even going downhill after getting stuck in 4th will not make 5th gear come back. The only fix I've found is to either pull off the road and turn the car completely off then back on, or to break the 100 mph barrier and sharply let off the gas, which still does not restore the tiptronic mode, which stopping the car will do. Has anyone else experienced this? Please Help. I've taken my car to the dealer, after testing they told me that if i'ts not throwing any sort of code or no warning lights are going off then they can't find the problem. I know that in the manual, it says that if the transmission gets too hot then manual mode will become unavailable, but what worries me is even after driving on flat roads after the hill, the transmission will not go back to normal.

 

from the owners manual...
If the automatic transaxle fluid (ATF) temperature becomes too high, there is the possibility that the transaxle will switch to automatic shift mode, canceling manual shift mode and
turning off the gear position indicator illumination. This is a normal function to protect the AT. After the ATF temperature has decreased, the gear position indicator illumination turns back on and driving in manual shift mode is restored.

does that sound like your issue?

 

It does, and I have seen that in the manual, except that I have driven (after the hill) on flat highway, just crusing for about 20-30 mins but it still never went back to normal. To further emphasize what I mean, If I crest the hill and confirm that the manual mode has been disabled, I can pull off the road and restart the car and have a normal functioning transmission. This of course being within the span of about 3 minutes. (without much time for the fluid to cool down) So what is different in these scenarios? It's not like the fluid can cool that quickly, especially while not even moving.

 

similar to fault codes, it may only lockout under certain conditions (high engine load + temp + time) for example.
But since there is no fault code for this issue - you said no engine light - so there may not be an available definition of the conditions to trip the fault. The dealer may have information on it, surely they could find out, though they probably don't have much of an incentive to. If you ask they will probably tell you that you need a fluid flush or something that they will happily do for $150.

So the overheat could still be the issue... i'm sure that partway up the hill is when it locks out the trans, so you could try manual mode a few points up the hill, then reset via turning the car off, and it should then lock out sooner if you continue up the hill.

 

this issue is on an automatic... that washer is a manual part