1985 5000s wagon five speed

[tripperjohn at webtv.net]

in heavy stop and go traffic shifting gets rough and clutch feels
different. Ok when car is over heavy stop and go but today I got a
clutch chatter in first gear. Car was cold and got to store. restarted
car started backing out of space and a very loud bang came from rear of
car. I stopped and coasted out of space put car in first and it never
shifted better and smoother since it happened. I'm afraid to take it
anywhere because no one seems to have any idea what the hell happened.
It was like something was hung up and broke free and the car runs and
shifts like as if it was new. I had a vibration over 55 mph that went
away after that bang.   I haven't  driven in heavy traffic yet though to
see how that is now. Any ideas? Someone said I might need a slave
cylinder whatever that is. HELP