I have a 97 ford f 150 4x4 automatic trans that has 84,000 miles. when I am driving at roughly 35 mph it begins shifting but does not always complete the shift. It seems to flutter a little between the gears? If I accelerate it shifts with no problem but if I am driving in the 35 mph area it does not make a clean shift. HELP!!!! The tranny fluid has not been changed in roughly 25,000 miles.

 

Hi wolson and welcome to FTE
Do you know which transmission your truck has? You can tell by the trans code on the VIN tag on the door. If you search here you'll find a thread that tells what's what or just post the code and someone will decipher it for you.
There are a couple TSB's on upshift problems that might apply depending on which trans you have.

I've also asked one of the administrators here to change your username for you. Having an email address posted anywhere online, in a username or signature or wherever, can be a bad thing. Some spammers use programs that search out email addresses and then they start firing off Spam to any they find.