i have a 1991 subaru legacy awd, automatic, car shifts fine untill it gets hot then only shifts one time, if i let it cool for a few hours it shifts great again.. trany fluid is nice and red no burnt smell..... also no check engine lights lit.....any ideas

Optional Information:
1991 Subaru legacy awd 2.2

Already Tried:
had trany flushed by valvaline