Well, technically, assuming that the old and new ball joint are manufactured perfectly concentric, you would be good to go. I would change them, and if it doesn't pull to either side on a test drive, call it done.
I have a 1996 F150 with a 4R70W, and here is a cut/paste from the owners manual:
If your vehicle is equipped with an Electronic 4-Speed Automatic (E4OD or 4R70W) transmission, operate in Overdrive. Refer to the automatic transmission operation earlier in this chapter.
When descending a steep...