use motorcraft automatic tranny fluid

 

If you use Royal Purple the only places I could find it at was a local speed shop and online.... I have never seen it in an autozone, advanced auto, etc.

 

as a side note: If you are going to change the fluid because you think it may solve your problems... maybe you should flush the tranny rather than just change the fluid. It obviously costs more, but it will flush out all of the old stuff along with some ugly sludge buildup.