So I know this isn't a hardcore rockcrawling question but it is important to me nontheless. The truck is a 99 super duty with the 5.4 motor, auto tranny, 100% stock.
The problem is that it shifts very hard and speratic (sp). Sometimes it shifts fine but other times it really shifts like crap. The truck has had the tps replaced 4 times due to thats what the ford dealership keeps saying is wrong with it.
I asked this question in gen4x4 and they said replace the vss in the rear axle. So thats what I replaced and while I was at it I changed the rear fluid also. The truck has 175,000 miles on it and they are all hwy miles. It has only pulled something a handful of times. It actually use to be my moms dd to and from work so it has been babied its whole life. I really want to figure out what the cause of the problem is because its still a good truck with lots of life left in it. Has anyone else had this kinda problems with their SD? Any help is greatly appreciated. Also the truck has been regularly maintained ie oil changed at 5k and air filter replaced as needed. Nothing has been neglected that I know of. I really thing it is the computer that is malfunctioning, but I don't know for sure.

with that many miles have you considered the tranny might be worn out? computer autos do all sorta of weird crap when they go. (the few i've had experience with)

dealers are a pain in the ass with intermittent problems. good luck

does the overdrive light flash?
mine did that and it was the shift control pack in the tranny

I dont think the tranny is gone in it because it still shift all the time. I dont know if it is the shift pack in it. I don't really know about that tranny. How do you go about replacing the shift pack?

Possible bad ground somewhere along the lines, try cleaning up your terminals real good and checke other grounds that are visable. Have has similar problems when the battery terminals get nasty. Just an idea. Good luck