Chatter - Shudder - Shake on takeoff in 1st

[Killermiller]

I've got a severe clutch chatter in first gear on the Bis. It is present only when the clutch is engaging; once engaged, it stops. Shift fines, no strange noises from the gearbox, no problem whatsoever.
A new spigot (pilot bushing inside the crank) perfectly cured the problem for some 2000 kms, then, slowly,  it developed again.
I've tought about 1) worn spigot bushing due to lack of lubrication (I forgot to put grease inside it when I reassembled the transmission), or 2) a faulty bushing. So removed the transmission again to check it, but it seemed to be ok. Also, the parts store that sold me the bushing said that it doesn't need lubrication, and the new spigot bush is a genuine Fiat spare.

Taking off in 2nd is ok, no chatter. No chatter in reverse, too.

Clutch cable inside or outside the bracket on the side of the gearbox won't affect the problem at all (made tests).
Throttle cable doesn't affect (tested with the choke on and the cable disconnected, it chatters the same).
I've replaced the motor mount. The transmission mounts and bracket are fine, too.
Flywheel? Clutch disc? (shouldn't a warped - glazed flywheel - contaminated clutch make the car shake in reverse or 2nd gear, too?)
Any idea?

[tim1968]

I had a similar problem. the gear box rubber mounts are held on by two studs sticking out of the gear box. the mounts were replaced but it still happened. it was then that I realised that the studs themselves had stripped the threads from the gearbox and it lead to more movement in the gear box which led to a lot of juddering when pulling away. a helicoil kit fixed it. May be have a look to see if yours are ok?

[Killermiller]

Hi Tim, thank you very much for your reply.
The Bis bracket is slighty different, it has four (instead of two) bolts that screw into the aluminium of the gearbox. They all are fine and tight.
Also, it seems to me that the shake is less present with engine (and gearbox) cold.