I know there are many knowledgable people on this site but this may take someone thats 'up to date' to answer.
My family car is a 99 Taurus.It is an automatic trans. I have noticed a slight stumble or hesitation while stopping due to what seemed like a delayed downshift. Today the trans.wouldn't shift out of low gear. I pulled over and checked the fluid level and it is fine and doesn't smell burnt. I started the car and it drove fine and I made it home.
One other note,,there has been times recently that the engine has had a rough or weak idle while stopping but the trans. requires no vacuum source that I am aware of. And I have read on the internet by typing in "Taurus trans.won't shift" that when the speedometer doesn't work that the trans.may not shift. My speedometer works intermittantly. Any replies will be greatly appreciated,thanks.