2002 f350 slow shifting 3 to 4

[gregmitchem]

I have an '02 7.3 f350 that often shifts very slow from 3 to 4 , I was wondering if anyone had any thoughts of a cause and also if a fluid change is advised, I bought the truck with 90,000 miles on it and it now has about 120,000. I do not how often if ever the fluid has been changed in it the first 90,000. I have heard in the past that it can stir up problems to change trannsmission fluid that has been in a vehicle for many miles.

[FordNutz]

How slow? It is a very common problem with these transmissions and why the installation of a valve body with a shift kit installed should take care of it.

[gregmitchem]

I am not real sure how to describe how slow, but it seems worse when I first drive the truck and it isn't real warm. I will often find that when it seems to be in 3rd too long if I let off the accelerator a little it will change. I am not sure what a valve body with a shift kit is