Date:         Fri, 7 Feb 1997 12:37:53 -0400 (AST)
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         smitht@unb.ca (Tim Smith)
Subject:      <Syncro>  viscous coupling fluid


Just an update for Syncro owners.  I'm trying to find a source for fresh
fluid for the Syncro couplings, Dow-Corning being first supplier candidate.
Got through to automotive division, they sell silicone based coupling fluids
with room temperature viscosity from 10,000 centipoise (about 90W at room
temp) up to 1M cp.  Some interesting data points, they supply the fluid to
Chryslers Jeep/Eagle Gear divisions for the diffs.  The basic stock Talon
gets a fluid of 10K cp, while the Jeep gets 88K cp.  The Talon racing team
gets 1.2M cp !!! Essentially locked up diffs all the time, enough slip to
allow cornering barely.  
Dow-Corning will provide the fluid at any cp value you want, 10K - 1M cp, in
55gal minimum orders.  In talking with the engineer I said I was looking for
a fluid that thickened as shear/slip occurred, but he said their coupling
fluids thinned slightly as shear increased and were mostly temp independent.
This is bass-ackwards from my understanding of the Syncros unit.  And from
how I would want/expect the fluid to behave.  Am I nuts? anyone want to help
out on this?  Any info on Jeep/Talons etc?

I have a vested interest in this for the Syncro natch, BUT my (Mech Eng
Dept) students are going to enter an SAE 'Baja Buggy' 4x4 competition, so I
can try for the coupling fluid as part of the project, multi-disc fluid diff
couplings being easier and cheaper to build than gear based differentials,
and give full 4x4 mobility.  The Dow-Corning engineer was a race inspector
for this event BTW, so he knew what I was intending.

So if anyone has more info on the fluid let me know!!!  I _think_ the Dow
guy will send me some (small) amount of fluid.... once I know what viscosity
I need. Food for thought, Tim