Rear differential lock always on

[Radek]

Thanks guys for all the input.  The diagnosis is now complete:  lever on the differential is moving freely.  Disconnecting the vacuum line that goes to the differential eliminates the problem.  So it was the rear diff, not the Torsen.

It looks like the source of the problem is with the differential switch, next to the handbrake.  Someone tampered with it, it has no connector and wires are soldered to the switch directly.  A good diff switch lying around, anyone?
Thanks.
Radek.


------------------------------

Message: 9
Date: Mon, 26 Apr 2010 09:25:26 -0400
From: "Louis-Alain Richard" <laraa at sympatico.ca>
Subject: RE: Rear differential lock always on
To: "'Robert Rossato'" <rossato.qlist at gmail.com>,
<audi at humanspeakers.com>, <quattro at audifans.com>
Cc: 'Radek' <radek at istar.ca>
Message-ID: <BLU0-SMTP51D1446403F95066C20D03CE040 at phx.gbl>
Content-Type: text/plain; charset="iso-8859-1"

A locked rear diff ? That's the easiest thing to test : find a parking lot,
turn left, open driver door, look for rear left tire spin.

If not, then it's the torsen bind.

Louis-Alain



-----Message d'origine-----
De?: quattro-bounces at audifans.com [mailto:quattro-bounces at audifans.com] De
la part de Robert Rossato
Envoy??: 26 avril 2010 07:08
??: audi at humanspeakers.com; quattro at audifans.com
Cc?: 'Radek'
Objet?: RE: Rear differential lock always on

Maybe it's a short wheelbase thing.  All I can say is that I've never
experienced that on any of the C4 chassis quattros I've driven.  With tires
ranging from snows to 255/40-17s.  Radek's problem could still be a locked
differential.

bob



-----Original Message-----
From: Huw Powell [mailto:audi at humanspeakers.com] 
Sent: Monday, April 26, 2010 2:17 AM
To: Robert Rossato
Cc: 'Cody Forbes'; 'Radek'; quattro at audifans.com
Subject: Re: Rear differential lock always on

ABS, haha, long dead.  Relay pulled, switch gone. The rear is not 
locked, everything is different when I do that.

Robert Rossato wrote:
> Hmmm, I wouldn't expect it to be a Torsen thing.  My S6 is essentially the
> same setup as the 90Q - Torsen center diff and lockable rear diff.  The
only
> time I have had shuddering from the rear wheels was when I locked the rear
> diff on dry pavement on purpose - just to make sure it was engaging.
> Otherwise she's quiet.  Full lock or not.  
> 
> Sounds like the rear diff is stuck in the locked position.  Is the "ABS
Off"
> light on by chance?  That comes on when you engage the rear diff lock,
which
> should disengage on its own at 15 mph.  If the light is on and it's not
> disengaging at 15 mph then it sounds like there might be something foofed
> with the vacuum switch.  If the light is not on, then it's possible that
the
> rear diff lock is internally stuck.  Try crawling under there and see if
you
> can engage/disengage manually.
> 
> Bob

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