car drives great up to about 45 min then doesnt like to go over 60mph without rpm hitting 4k any thoughts? I drained and filled and put lucas transmission treatment in it. would a bad tranny cooler do some of it or is tranny dying.? sensors? programming? any thoughts. Bought the car a month ago and

Did you ever figure out what it was? Mine does the same thing. Mine drives perfect until I get around 40mph then it just revs high to continue speed. I’m wondering if it’s because TC isn’t locking into high gear.