afidel wrote:
Be careful with the transmission flush, if it hasn't been maintained with regular changes you can actually cause more problems with a flush and fill then you solve.
Old wive's tale that stemmed out of happenstance rather than actual causation. Those failures wre coming, whether the transmission was serviced or not.
Just do a drain and fill, changing the filter when drained. I did this to my 1997 E150 van (same setup, 5.4, auto, 9.25 sterling rear), but I put in AMSOIL synthetic. The van shifted like new after that all the way until I lost it in the divorce at 302,000 miles. I towed a LOT with it, too, mostly a 5x14 enclosed cargo trailer, but the occasional flat deck.
Chemical flushed are unnecessary 100% of the time. Snake oil.