I have a 1991 5spd Civc HB.

When I drive at a constant speed and let off the gas
suddenly. the entire gearbox shakes. Something up
front feels really loose...

I wonder if one of the motor mounts or transmission
mounts is shot?

Also, first thing in the morning, for about 5min, I get
some clutch chatter, and the entire car shakes. After
that 5min it goes away for the entire day...

Any Ideas?