clutch / gear grinding / ugly sounds

[andrew]

My '70 SIIA 88" was working just fine...yesterday.

This morning it was shifting only with some effort into 3rd and then once or twice did not want to go into 3rd at all. Then, it on occasion from a stop would not want to go to 1st (or 2nd) -- the gears were spinning quite fast it seemed and there was no way to get it synced up and into gear without grinding off all the teeth (or so it would seem, I of course did not force it). I actually had to shut the truck off, shift into gear when it was stopped, and then start the truck up again to get away from a dead stop. I drove home this way (3rd seemed to work for the most part), though at one stop sign things worked fine, but then back to grinding again. So, it would seem that the clutch is not disengaging the clutch plate/pressure plate from the flywheel, for whatever reason (seems to me...). I suppose the problem could be with the throwout bearing, slave/master cylinders, or something else. Thankfully (or sadly), I'm not a clutch expert by any stretch, yet...but I'm thinking I will need to be soon.

By the way, double-clutching did not help.

Did my clutch or the components mentioned above just go bad? Does that happen so suddenly? The sudden and intermittent nature of the problem confuses me (but it's not intermittent now...just does not want to get into gear without grinding like hell). Where should I start, with the logic of looking into the simplest/cheapest/most likely culprits first? Other thoughts and ways to diagnose/fix?

Thanks for any help...much appreciated.