Need some tranny help

[Tonykoser]

Need some help. Just purchased a 1991 f450 with a automatic. Drove it home, about 120 miles. Truck ran fine but I noticed that the converter would not lock under normal driving conditions. If I put it under a heavy acceleration it would then lock but as soon as I stopped accelerating it would unlock. This is backwards tranny should unlock under acceleration and lock up under a normal load

Thanks in advance

 

[Thewespaul]

Check your fipl voltage, there is a tech article on the procedure under the idi tech articles at the top of the page

 

[Therkhan7_3Turbo]

https://www.ford-trucks.com/forums/...-and-adjustment-diesel-applications-only.html

I have it in my bookmarks. I reset mine just a bit and it made my shifts go from redline and full line pressure ( no matter what ) to almost a 99/00 truck... smooth, shifts, at a reasonable rpm.