RE: 87 4kcsq center diff lock problems.

[Keith Bedard <KBedard@TDPC.COM>]

I have your answer -- DIFFERENTIAL SWITCH CHECK VALVE!

I went through this with my '87 5KTQ for 6 months before finding the
solution. It basically turns itself on and off, and when the lights are off,
you know it is still engaged when taking tight turns. 

This check valve is located behind the differential control, under the
radio. Just take off the side panel for the center console, and there it is
- your basic white plastic check valve with two outlets: one for vacuum
coming in, one for vacuum coming out. One outlet on the valve connects to a
vacuum line from the motor, which activates the vacuum line going to the
locking lever coming out of the differentials. A check valve should only
allow the pass of air in one direction, so you will pull this out and see
that you can blow or suck air out of both ends, meaning it is garbage. 

I inquired about the price to replace this. It is absurd, around $40. Your
best bet is out of a junkyard, mine was replaced with one out of a wrecked
V8 Quattro. (It was a litte different in that it had three outlets instead
of two, but you can just seal one outlet). Anyway, I believe most check
valves of this nature pretty much accomplish the same thing, and work the
same way, so you can probably get one out of a Ford or GMC, and they might
work. But in the long run, save yourself time and frustration and grab one
at a junkyard.

p.s.
Two dealers couldn't pinpoint this problem on my car. My engineer friend
who's an ex-Audi mechanic figured it out. I have to give him credit --
Thanks again, Mike!

p.p.s.
I have a message to send to the list, have tried twice, but it has not been
listed. I have simply been emailing "quattro@coimbra.ans.net" Is this the
right method?

-----Original Message-----
From: Jamie Hayes [mailto:jhayes@lawnandleisure.com]
Sent: Tuesday, December 22, 1998 1:31 PM
To: quattro@coimbra.ans.net
Subject: 87 4kcsq center diff lock problems.


AHHHHHH, Quattro.  This is the first time I've actually had to "use" it
since I bought it a year ago.  Everything's worked fine up until last night.
I locked the center diff to see what difference it made in the car's
handling.  What I got was a diff lock that kicks on and off at will at a
fairly regular interval.  The light goes out and you can feel it disengage.
Then the light comes on and so does the center lock.  Any suggestions??

Jamie