Bad slave cylinder?
 

I backed out of my buddy's driveway the other day, and I heard a loud CLUNK-like someone hit a cinder block with a steel pipe, and my clutch pedal went all the way to the floor. I shut it off, and pulled the pedal back up-it moved freely. Now, the pedal won't depress. I can still put it in gear when it's turned off, and if I turn the key it takes off. Never had any clutch slipping before. I'm assuming it's the slave cylinder, but wanted to hear some second opinions first, as I am NOT a motorhead, and know very little about transmissions, linkages, clutchs, etc. The brakes work fine, so I'm assuming the master cylinder isn't the problem. I did some Search-Fu around here, and it sounds like if it is the slave, I should change the master at the same time.

It's a non-turbo 1985.5. The motor was replaced with an '87, so I'm not sure what year the clutch is or if there is any difference between those years anyway. Hope I gave enough info!

Typically slave cylinders don't make clunks when they fail, the pedal just goes to the floor and stays there. You can push the pedal down again, and it will stay at the bottom. I have never seen one seize up like that before. Sounds to me like either your clutch fork, or clutch fork pin broke inside the bellhousing.