89 Vette clutch knock

I bought an 89 Vette 5 months ago with 15,000 miles on it. After driving it about 1,000 miles I started hearing a knock at warm idle. The knock kept getting louder and starting earlier (I used to have to drive 30 miles or more before it started knocking, now only 5 miles). It knocks weather the clutch is in or out, in gear or out. The knock goes away when clutch is let out in gear. This is a 6 speed with the 1 to 4 solenoid disconnected. I pulled the tranny yesterday 03-19-2005 but haven't inspected clutch yet. Any suggestions?