Date:         Wed, 23 May 2007 12:57:58 -0600
Reply-To:     Richard A Jones <jones@COLORADO.EDU>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Richard A Jones <jones@COLORADO.EDU>
Subject:      Syncro propshaft vibration mystery
Comments: To: Syncro@yahoogroups.com, syncrolist <syncrolist@yahoogroups.com>
Content-Type: text/plain; charset=ISO-8859-1

I need help finding the source of a vibration in my '87 Syncro.
It started coming home from the Arizona Bus Roundup in '06.
It feels like driving on the "wake up" strip along the edge
of the lane, but it starts at 25, fades at 55+, comes back at 70+.
So 60-65 is a sweet spot with no vibration.  I think it comes
from the front, since I feel it in the seat, floorboard and
the steering wheel.

It is not wheel speed, it is faster.  Two 5-tire rotations
and wheel rebalance show it is not tires/wheels.  All half-
axles appear good with no CV problems.

Removal of the propshaft eliminates the vibration.  But two
known-good propshafts, one a brand-new GoWesty, show it is
not the propshaft itself.

I put in 6 new rubber mounts on the front diff and made a laser
alignment tool to check the alignment of the tranny and the
front diff.  Before, there was a very small horizontal misalignment.
Now there is none.  Vertical difference is 8.5 degrees--not very
much. Front diff points down 2.5 degrees; tranny down 6 degrees.

Mounts and alignment made no difference in the vibration.  Now
I am stumped and don't know where to look or what to do next.
Any ideas?  Any experience with a problem like this?  Help!

Pictures of the alignment tool I made (simple) and its use are at
http://jones.colorado.edu/jones/SyncroAlign

[BTW--Jorick Vandaele's post of May 9th on the syncrolist citing
http://www.baileymorris.co.uk is very valuable.  Under Technical
Info are some pages that show why the drive/driven have to be
aligned in two planes and can handle difference in the third.]

Richard
Boulder