I saw a post with similar symptoms and the poster found that the cable to his kickdown switch was crimped and when he corrected it, it started shifting correctly. I am tracking down all the angles to this quirk, I think there is also a kickdown relay on the tranny, not sure though. The tranny was replaced 2 yrs ago and I'm wondering if it was ever set up correctly. If the kickdown relay is on the tranny they might not have hooked it up. This car literally was granny's ride around town so I don't think anyone would have complained.
And yes, I am waiting for Steve to weigh in on this...