Rear locking differential 1988 90Q

[Radek]

I had to grind down the pivot pin to separate the arm because it was a clump 
of rust, but now that the actuator is out I can clearly see the side facing 
the differential - there are more cracks there, all caused by rusting 
attachment screws.  New MB part will go in there.  My only concern is the 
metal crescent-shaped shield the actuator is attached to, it is quite thin 
because of rust.  I'm thinking of reinforcing it with a layer of fiberglass 
so the acuator can be firmly attached.  Thank you guys very much for your 
help, without you I wouldn't be able to figure all this out!

PS:  do you know a good (read:  cheap) source of differential mounts? 
Worldpack sources don't have it, dealer sources are pricey.
Thanks again!

Radek.

>
> Message: 1
> Date: Tue, 7 Aug 2012 13:47:52 -0400
> From: Louis-Alain Richard <laraa at sympatico.ca>
> To: "'Radek'" <radek at uniserve.com>
> Cc: quattro at audifans.com
> Subject: RE: Rear locking differential 1988 90Q
> Message-ID: <BLU0-SMTP30803246622678F775384DCECE0 at phx.gbl>
> Content-Type: text/plain; charset="iso-8859-1"
>
> The shorter version of the adress...
>
> Sorry.
>
> http://www.audifans.com/pipermail/urq/2007-December/012483.html
>
> Louis-Alain
>
> -----Message d'origine-----
> De?: quattro-bounces at audifans.com [mailto:quattro-bounces at audifans.com] De 
> la part de Louis-Alain Richard
> Envoy??: 7 ao?t 2012 13:44
> ??: 'Radek'
> Cc?: quattro at audifans.com
> Objet?: RE: Rear locking differential 1988 90Q
>
> Just found my old post from december 2007... on a French Audi forum !
>
> You also need a die to retread the metal shaft...
>
> http://webcache.googleusercontent.com/search?q=cache:xYLlaL4kimIJ:www.audifans.com/pipermail/urq/2007-December/012483.html+000-800-6
> 9-75+or+123-800-33-75+mercedes&cd=1&hl=fr&ct=clnk&gl=fr
>
> Louis-Alain
>
>
>
> -----Message d'origine-----
> De?: Radek [mailto:radek at uniserve.com]
> Envoy??: 7 ao?t 2012 13:01
> ??: Louis-Alain Richard
> Objet?: Re: Rear locking differential 1988 90Q
>
> Super, thanks!  Two questions:
> 1. Are screw openings (3) spaced the same as in the Audi?
> 2. Can the actuating arm (transparent plastic in the MB, metal with rubber 
> boot in the Audi) be pulled out of the actuator without
> breaking something inside?
> Radek
> Ottawa, Canada.
>
> ----- Original Message -----
> From: "Louis-Alain Richard" <laraa at sympatico.ca>
> To: "'Radek'" <radek at uniserve.com>; <quattro at audifans.com>
> Sent: Tuesday, August 07, 2012 12:08 PM
> Subject: RE: Rear locking differential 1988 90Q
>
>
> The leak is often in the rubber boot over the actuating arm, hence the 
> partial failure. The diaphragm is OK.
>
> Repair is difficult since the plastic is very brittle and the boot is not 
> available separately. I use some Mercedes-Benz door lock
> actuator from the mid-80s on my urQ. Almost identical, except for the 
> color (MB black, Audi beige) and probably plastic material.
> You'll have to swap the plastic connector from the old one. Otherwise, 
> they work well.
>
> 40$ here : https://mercedessource.com/node/1286
>
> Louis-Alain
>
>
>
> -----Message d'origine-----
> De : quattro-bounces at audifans.com [mailto:quattro-bounces at audifans.com] De 
> la part de Radek Envoy? : 7 ao?t 2012 11:29 ? :
> quattro at audifans.com Objet : Rear locking differential 1988 90Q
>
> So now that the diff is out, we can clearly see the cause of it being 
> locked all the time.  As I suspected, the plastic vacuum
> actuator has broken off at one of the three screws and is moving around a 
> bit.  I used a vacuum pump:  it seems to be holding vacuum
> when the "on" side (yellow striped hose) is activated, but doesn't hold it 
> when the "off" side (blue striped hose) has vacuum
> applied.  This is odd, because I would expect a single membrane inside, so 
> if it's broken there would be no vacuum held on both
> sides.  To put things differently, the actuator has enough strength to 
> engage the lock, but not enough to disengage it.
>
> I would like to take it off the diff to clean, inspect and repair/replace.
> Here's the question:  how do I separate it from the diff?  The actuator 
> arm has a pin at the pivot point, but it seems to be
> permanent.  Can I pull the arm out of the actuator or out of the 
> differential perhaps?  Bentley does not offer any help (or I
> haven't found it).
> TIA
>
> Radek.
> _______________________________________________
> quattro mailing list
> http://www.audifans.com/mailman/listinfo/quattro
> http://www.audifans.com/kb/List_information
>
> ------------------------------
>
> Message: 2
> Date: Tue, 7 Aug 2012 12:51:07 -0500
> From: Tony Hoffman <auditony at gmail.com>
> To: Radek <radek at uniserve.com>
> Cc: quattro at audifans.com
> Subject: Re: Rear locking differential 1988 90Q
> Message-ID:
> <CAJM_R3o-u-Wa-N4LmjV+tMqyLC_KQ0h3dyVPx-7B0Fgr8Ef-Jg at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
>
> I've repaired several of these. First thing to do is figure out where it's
> leaking on the "off" side of actuation. Is it leaking at the broken off
> tab? Is it leaking out of where the boot should be? I've repaired the
> missing boot with a rubber cover designed for the end of a silicone tube.
> However, they disintegrate after about a year, so I'm not too sure what
> I'll do long term.
> Here's a pic:
> http://littleredcap.com/
>
> As for the crack, I've used epoxy from teh inside and outside, and had
> really good results. The part where the pin goes on, that unscrews from 
> the
> rest of the actuator. You will have a stud left sticking out, that is not
> removable. It's part of the rubber bellows that actuates the lock.
>
> HTH,
> Tony