Originally Posted by 99 f350 PSD
when pulling cattle trailer or with no load the trans does not want to shift like it should seems lazy. i hear what sounds like a hydrolic whine until it gets to overdrive.the trans seems to shift better if your foot is on the floor. just changed trany fluid and filter and that did not help used mercon V.
Check your dipstick's yellow pull ring. It'll say either use MERCON or use MERCON V. The reason I ask is because if the stick says to use MERCON, you can't use MERCON V. The reason being is, a good percentage of the 4R100s from e'99 to 2001 were built with a lighter-duty coaster drum version that are found in all E4ODs. Even though it's safe to use MERCON V in most of Ford's transmissions, it doesn't work as well with E4ODs or 4R100s with these outdated coaster drums.
Check your dipstick & let us know what it says. If it DOES say to use MERCON V, we'll move on to the next possibility.