The truck had just recently lost pressure in the clutch, when it hsppend I check fluid topped it off ended up to the rim. Had every little presser enough to get me home.... now none I see no leaks from inspection hole clutch seems ok.... fluid still full... any suggestions

 

The reservoir should not be filled to the rim. I would make a wild guess that there is a slight leak at the slave cylinder.

 

If you don't see a leak at the slave, it may be the master cylinder.