<VV> RE: I'm pickin' up weird vibrations....

[Western Canada CORSA]

...my 'vairs give'n off not so good sensations.

Drove the 'vair up to Port Alberni today.  On the way back I picked up a
very strange vibration.

car is a '66 140/4spd, bolted flywheel and dale balancer.  Otto rotated
carbs.

Engine feels good, pulls strong, holds strong.  But at anything over
3000rpm, in any gear, when I left off the gas I get a thrumming harmonic
vibration that comes through the pedal in particularly.  When I let the
engine freewheel and rev it, no vibration.  Letting off the gas below 3000
and all is normal.

My first three guesses are:

1) u-joints (6yrs old),

2) clutch, which is also 6 yrs old and doesn't particularly have a ton on
miles on it.  It doesn't chatter when accelerating from a stop, but could it
be oil on the clutch?

3) crankshaft (please no!)

Oh all mighty gurus of Corvairdom I plead for your magnificent wisdom.

Regards,
Joel