I have a 2002 F250 Super Duty with a 7.3 Diesel. My problem started on Sunday when I was going up a steep hill on the freeway. I could not accelarate and the hill that I usually go up at 65-70 drug me down to 50. I also noticed that the truck did not come out of overdrive. On Monday it was worse. The truck dropped to 35 and would not shift. I got home and changed the fuel filter and that did not help. It actually slowed down more on a test drive after the filter change. Tonight I added a quart of trans fluid and that seemed to help some. Any other suggestions?

 

Welcome to FTE.

Look at and smell the fluid for off color or burnt smell. When was the last flush and filter change. Thes 4R100 trans are the weak point of our truck. I would change the oil and filter, then see if that helps. If not, take it to a good tranny shop and let them have a look at it.