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?

 

Mine did that, the clutch hub springs were totally dead, I had to replace the clutch anyways, so I went with a CM stage 3 and have no problems anymore.

Shake springs, shake...

 

Agreed, hub springs. If you want an inexpensive replacement, you can get an Exedy OEM or Sport pressure plate and and disc for $110/$260.

What language are you speaking at the beginning of that video?

 

it's DeeJay [Drunken Jibberish]