Here's the problem, when my 84 Z28 H.O. w/ T-5 transmission is running, and the clutch is pushed to the floor, the shifter will not shift into any gear unless forced, and when I attempt to put it in reverse, it just grinds. However when the car is off, it will shift smoothly through each gear.

I have a centerforce dual friction clutch and a hurst shifter, both installed approx 6000 miles ago, the transmission and these parts have never given me a problem before, the car has 115,000 miles on it.

 

Sounds like your hydrolics are going out. Try bleeding the system and if that doesent work it would be a good idea to replace the Clutch master and slave together.

 

forgot to add that the slave cylinder was replaced approx 30 miles after the new clutch was installled... it failed. Is it possible that this failed again?

 

Let me fill in a couple of blanks for you. Stop me if I'm wrong. (if what I'm saying is wrong, that is; I already know I'm wrong)

It worked fine, then the old clutch wore out or whatever, then you put in a new clutch, and it did this; and no amount of jacking with the hydraulics has changed it.

Right?

Check this thread, just below yours; and see if those pictures tell you anything.

 

yes the original clutch was replaced because it was wearing out (the old clutch settup worked fine)
The new centerforce clutch was installed and the slave cylinder went after approx 30 miles, and has worked flawlessly for the past 6000 miles or so.

This happened after pulling into a parking spot... however I started the car today and it was fine. My main worry is that this is a warning, and it will happen again.