I have a 2010 5.4L F-250 that has the six speed in it. I bought it used with 16k on it. Ever since I owned it, it will occasionally pop out of third gear and grind when you try to put it back in. At first I thought it was just me not pushing it up in far enough, but it's been happening a little more frequently.
Unfortunately, it's not repeatable. It happens during random temperatures and under various load conditions.
I just dread taking it to Ford, when I can't even show them the problem. It is Ford Certified so the powertrain is covered to 100k.
does it seem to just pop out when you're just cruising or let off the throttle? that usually indicates a posssible bad pilot bearing letting the main shaft wobble around. other wise it probably a broken set of syncros.
could be a damaged sliding shift collar. either way its not right. you have nothing to lose by asking if the tranny is covered and telling them to fix it. if you have the tranny down I personally like to at least look at the clutch to see how much life it has left. dropping the tranny is 95% of clutch replacement labor
If the clutch is bad at 16k that could very well indicate a problem with the tranny. Have Ford look at it. If nothing gives them an indication there is a problem you might have to live with it untill it becomes a problem. Did you/they do an Oasis report before you purchased?