Ford 7.3L Power Stroke (1999-2003) :: Clutch Pedal Would Squeak While Coming Off The Floor?

What is failing. I have a 2000 F350 PSD with 116k miles. When I bought the truck last year, I noticed that the clutch pedal would squeak while it was coming off the floor. It doesn't happen when the engine is cold. I need to drive it about 30 min before it starts to happen. On longer trips, several hours, the squeaking is louder and the pedal gets very stiff. When I stop for fuel, I've come close to stalling when coming out of 1st gear. I can push the pedal to the floor, but on the way up, the pedal squeaks, and then once I reach a certain point, say 3-4 inches off the floor, the pedal looses all freeplay. The best way for me to describe it is the pedal travels up faster than it normally does when it's cold, and if I don't compensate with more throttle at that point, it will stall.

I've learned a lot by reading this forum for the past year, but I don't know the first thing about how to diagnose problems like this. I've taken it to 2 mechanics for test rides -- one thinks the clutch is fine and thinks the problem is the slave cylinder or a broken bushing in the pedal.

The other shop is also a small independent shop, but they specialize exclusively in Ford trucks, so I thought they would be more knowledgeable. But now I'm wondering if they could sense my ignorance and are taking advantage of the situation. They also took it for a drive, but they think the slave cylinder is fine and that the clutch needs to be replaced. I questioned him about the slave, and he pulled it to look at it, and asked me to push the pedal slowly while he was under the truck. I still had a little resistance and a faint squeak even in this situation. But he said the hydraulics are so simple that he felt we could rule that out. I can't remember exactly what he said, but I think he believes one of the springs in the clutch plate has failed. I just know they are suggesting a new clutch and they want to machine the flywheel to original specs.

I thought the leading symptom of a failing clutch was slippage under a load. So under strain, I would expect my engine to race occasionally, like I'm in neutral. But I've NEVER experienced anything remotely like this, even when driving hard in the hills pulling my travel trailer.

I know something is wrong, but based on my limited knowledge, I'm not sure what. It's getting a little harder for me to move the shifter into 1st and reverse, but once it's there it's fine. I've never experienced any racing or slippage in any gear. The one definite symptom I have is that squeaky pedal that when driven for a couple of hours, gets so stiff that it can cause near stall outs. With those symptoms, what do you think is going wrong?