227,000 miles, 4.3 liter with a 5 speed on the floor...running 72mph down the highway today and got a sudden start of a whine so loud it drowned out the radio. (I know, turn it up) A rest area was handy so I pulled in, finding in the process that I could not downshift and the clutch pedal didn't feel right. Upon parking, there was no clutch pedal until near the very bottom. Releasing the pedal got a pretty nasty whine and grind. I called a wrecker since I was more than 60 miles from the house. After arranging for the wrecker I was messing with the clutch/noise/shifting...the pedal resistance returned to 'normal' and went to a more gentle rattle from the clutch/transmission area when running, clutch released and in neutral. The clutch seemed to respond correctly and allowed normal shifting and movement of the truck in the parking place. I have only driven it in first/reverse since, but there is a pretty healthy whine still which does change with speed. The only thing I did under the hood while waiting for the wrecker was to pop the cap on the clutch reservoir, which spilled fluid like it was overfull...which of course it can't be full beyond the lip of the container in the first place. I'm guessing something to do with heat? just because the clutch action returned after sitting a bit, and likely the throw out bearing? Any thoughts appreciated.