I have a 99 f-250 with the 5.4 and the 4r100 transmission. It recently stopped wanting to shift into second unless you rev it to about 2500 rpm and let off the throttle. It shifts through all the other gears fine and doesn't slip or have any other issues. It will also shift from 1-2 manually on the column without any problems. I've tried to look this problem up but can't find any answers.

 

I suspect either the intermediate one way clutch or the intermediate friction clutch is failing. The only way to fix it is to replace it, and that takes a rebuild.