On my 2000 with a 4.0 every once in a while my clutch will not want to release but it is always varying on how hard to get into gear it is (like some days you can just tell and 2 days ago with the clutch in the truck would roll on the level from the drag and I had to shut the truck off to get it in gear). I don't think it's the slave since it isn't leaking and I can't see a slave doing that, either it works or it doesn't, so I am wondering if its the master cylinder. It has me stumped because common sense tells me it should be constant, that's the way it was when I had to put a slave and master cylinder on my grain truck.

 

mine used to do the same thing, the slaves wear out and even though it wasn't leaking, it was definitely not moving through it's entire travel like it was supposed to. it's the slave, replace and drive

 

id try bleeding the system first and see what happens

 

i highly doubt its the slave. i am having the same problem. all signs are pointing to the master cylinder