105 GT Driveline Vibrations

["Jeff Greenfield" <alfaguy@domain.elided>]

I wonder if anyone has any words of wisdom on this one ...

I've been chasing a driveline vibration on a '67 Giulia Spring GT (105
series) for quite some time and have little luck eliminating it.

The vibration occurs mostly at higher speeds (>60mph) and is
particularly noticeable on deceleration when you back off the throttle.

The clutch was replaced and balanced along with the flywheel as an
assembly. The driveshaft was re-furbished (flex joint, u-joints, center
bearing and support, and was balanced). I then replaced the driveshaft
with another from a parts car all to no avail. 

When I installed the second driveshaft, I replaced the bushing in the
front of the driveshaft as well.

All of this has had little effect on the problem.

I've since discovered that there is what appears to be excessive wear
and run-out (Approx .010") on the spherical bushing that is actually the
end of the mainshaft on the transmission. This fits into the bushing
that is pressed into the front of the driveshaft.

My question is does anyone have an opinion as to whether this could be
the cause? Keep in mind that both this part and the driveshaft rotate in
unison so this serves to center the driveshaft in relation to the
transmission.

I think that this could be the cause of the problem bit would welcome
any other opinions.

TIA,

Jeff - Crew Chief Dovetail Racing ITB Alfa #42
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