i have a 01 quad cab with a 318, 94,000 milesand i rarely get to drive it because i have a work vechicle. Recently i went to drive it and when i started out it seemed sluggsh at the start. I get rolling good and it upshifts fine. Then sometimes it will go into first and not want to shift out. I went and changed the filter out and only had to add five quarts of fluid. after i changed the fluid and filter nothing seemed to change. i could assume the worst and say it was one of the clutches going out or would something simple like a total fluid flush or changing out the governor pressure sensor fix it. any advice would help because i've hit a mental block

 

it could be because you havent drove it in a while, auto trannys can sometimes do that when you dont drive them a while, how long did u drive it for, what was in the box, was anything on the hitch, hills, ect