My zf6 in a 2004 ford f250 6.0 powerstroke has been popping out of 4th gear (4th according to fords labeling on the shifter). It will then usually not go back into gear. At least for a little while. It does not grind when you try to put it in gear. Any ideas? I am think pilot bearing from what I have read on here. What do you think?

Seems this truck likes to show its problems right before I need it for a longer trip.....go figure.

 

Anyone have any idea?

 

Anyone know a part number or anything like that. Everything I have searched seems like it is a common problem but no one really mentions part numbers or where to buy them.