I own an 87 Vette with a 4+3 transmission. I had the cluth, throwout bearing, and pressure plate replaced 2 yrs. ago. I'm having problems with the hydraulic clutch. The pedal goes all the way to the floor. I can't shift gears, and the resivoir is full. Unlike a mechanical clutch, there are no adjustments for a hydraulic cluth.

Any recommendations as to what the problem may be?

 

Safe guess you have fluid leaking somewhere - look where the bellhousing meets the tranny, and where the bellhousing meets the block, and follow the lines as best as you can from the bellhousing opening back to the master cylinder. Check also under the dash where the MC pushrod pedal goes through the firewall.