stutter between 45 and 60mph
2001 F-150 supercrew 4X4, with a 135k miles. It just developed a stutter between 45 and 60mph. Not easily detected in 1st and 2nd when accelerating normally, but present in or out of "tow / haul" in 3rd gear or Overdrive.
If I deliberately hold the truck in 2nd gear I can get the same reaction in this range of 45 to 60mph, although the stutter seems a little supressed under that kind of throttle.
If it were a fuel filter, I thinking I would have to use a certain amount of fuel before encountering the problem at all.
It feels like maybe a converter lock up issue or transmission related.
What do you think?
Thanks for any help.