Anyone with thoughts here?

I have a friend who has a 2005 Buick Rainier that had rear air bag
suspension on it.  As seems the case, it developed a leak in one of the
bags.  In that no tow use would ever be made of it, the decision was made
to convert it to coil spring suspension.  Which, as I sort of watched the
darned good fellow do this, was done one side at a time with no strange
axle dropage or twist anywhere on the rear end.  Everything seemed to go
fine.  Except that now,for the first time on this 67,000 mile vehicle,
there is what I am pretty sure is definite driveshaft vibration that has
shown up!  It starts to be of notice at about 62+ MPH and then sort of
vanishes at about 75 MPH.

I wonder if it was really 'there' with the air bag suspension, but was just
never of notice then?  The shocks were also replaced with the reccomended
new ones at that time to.

OK, I have a friend who has done driveshaft alignment and checked U-Joints
for me for about 30 years now.  Very rare need but then, I built my
original Austin Healey 100 with a full Chevy Fuel Injection Corvette engine
in it back about 1962 or so.  And that, of course, meant a full custome
drive shaft for the Chevy Corvette transmission to the Healy rear end.  And
yes,I do understand about absolute need to align the U-Joints correctly at
either end of the shaft.  As well, as, in theory, to get the EXACT rear end
and crankshaft allignment with the rear end suspension so that they are
precisely alike in planar mode even as the axle bumps up and down.

But obviously, in the case of this Buick I don't do that design, nor was
there any change in axle positioning or whatever with this job.

So .. I take the Buick to my friend.  He jacks it up.  Oops!  It has an
aluminum drive shaft!  I've never seen this before and he tells me he
cannot check, straighten it.  As well, yes, I've had drive shafts custom
balanced in Houston a hundred miles South of me in College Station, Texas.
But welding balance weights and fooling with aluminum tubing?  Hmmmmmm...

Who should I listen to as to what they tell me about this?  What are the
thoughts here?

Thanks!

Mike Luther {at} 1:117/100 .. also N117C


---