97 park avenue trans problem
 

i have a 97 park avenue with 70,000 on it no supercharged, its been running fine little bit of a hard shift everyonce and a while, but yesterday the trans started slipping bad. if you let it sit for a little while and cool off it will go right into gear and shift threw all gears fine even reverse untill it gets warm then it loses everything including reverse also but will still go into park, it did have a little whinning sound from the trans and there is no leaks at all, the fluid is a little dark more brown grayish color than red doesnt smell burnt, also had a p1811 code that would not trigger the light in instrument cluster, i think i have stated every issue it has i dont really want to tear into the trans if i have to, i was wondering if it was a possible pressure control solenoid/valve or if anyone else has heard or experienced this same issue, thanks for the help

Was the fluid and filter ever changed ?

dont know the history just bought the car a few months ago, didnt want to change it and have to redo it if it was a valve problem and have to rechange it again