<VV> Rear end/axle noise

[Barneck Doug C TIGTA]

My sons 65 Corsa vert is making a noise in the back end.  It has a 3:55
posi rearend with 4 spd trans.  Both have been rebuilt by a very
knowledgable Corvair expert.  When he slowly starts out he is getting a
ringing coming from the rear axle shaft/drum.  The ringing sounds like a
resonance of the axcle shaft.  The u-joints are brand new spicer joints
but could possibly be bad after 50 miles.  There is no play in the
u-joints when elevated and turned back and forth.  If I stand to the
side, He just has to barely move and I can see the rim actually
ring/slip as it moves forward.  It is a repeated sound, not like a one
time bang from a u-joint.  More like you had brakes on all the way and
trying to move it and it will turn an inch at a time in jumps.  I have
backed off the brakes to verify that they aren't hanging up.  I don't
get any play out of the u-joints.  I am thinking that it is the posi
plates binding up and not slipping.  My son said if moving straight
forward it doesn't do it but just a little to the side and it will make
the noise.  It does not seem to happen when moving faster that 2-3 mph.
I don't think I forgot to put in the posi-additive but that was my first
thought.... Any other thoughts, insight or things to look at?

Doug Barneck