Date:         Fri, 7 Feb 1997 21:34:00 -0500 (EST)
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         SyncroHead@aol.com
Subject:      Re: <Syncro> viscous coupling fluid

In a message dated 97-02-07 11:41:33 EST, smitht@unb.ca (Tim Smith) writes:

> 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?

>From your description, their fluid is clearly not the type used in the Syncro
coupling.  The Syncro coupling fluid (just as you are thinking) is normally
at a low viscosity and when shearing action occurs, rapidly heats and becomes
highly viscous.  I don't have the chart with me, but if I recall, the
temperature at which this occurs is fairly high, like over 200degF and the
span from nearly open differential action to nearly fully locked action is
quite small like 20degF.  

Ths Syncro viscous coupling acts like an automatically locking differential
with a fairly short modulation duration between open and locked.
>From the description of the Jeep/Talon fluid it sounds like that unit acts
like a limited slip differential, with the amount of slip determined by the
viscosity of the fluid chosen.

Regards,
Jim Davis
87 GL Syncro
88 GL Wolfsburg