2002-05 Owners. As of August 2022 there is now an entire suspension kit for sale! Scroll down to the bottom of the first post click here.
Did you disconnect or replace your battery recently?
Read @doug7740's post above. Also, this thread discusses hard shifts- https://forums.fordthunderbirdforum.com/threads/transmission-shifting-rough-2004-thunderbird.7821/
Would love to hear more on this. I just got my fluid changed and it still does some shift flares and hard manual shifts after the fluid is warmed up. Did you drain out and pump in Lucas?have you changed your Tranny fluid and filter?
I have had success with Lucas Trans Fix additive.
Hoping this is the clue I need. 2004 PCR hard shifting into reverse. What state are you in and is there any chance you have the part info for that chip on a receipt from the repair?I had a similar problem. Ford dealership replaced a transmission computer chip (yes, they have a computer chip at least that is what I was told) and that fixed my issue.