94 f250 wont shift while driving

Tranny's probably shot

I can shift manually

I would definitely check the MLPS (Manual Lever Position Sensor) as they're exposed to the elements and road grime. They wear out and become a very overlooked, simple repair/replacement. Check the plug @ the mlps and the harness itself where it goes over the trans. I've seen lots of crap damage the wiring harness up there from people driving sheet metal screws through their floor (mounting stuff) to unseen damage from wheelin', though how you'd miss that I have no idea. Anyway, I'm sure there's probably a million youtube vids on how to change it, if you even need it, but if I recall from the last auto-trans Ford truck I had, it's mounted to the trans where the shift linkage is, behind the "ball" , by either 2 or three nuts.