Lockable Rear Differential Info for the S2, RS2, 92-94 UrS4 and 95 UrS6.

[A80Avant]

It does , I found a t piece after the check valve which is meant to lead and connect to a vacuum canister located in the rear quarter panel.

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[newsh]

[newsh]

vaccum leak found!
which also means that a boost leak is also sorted

Good stuff

[newsh]

also just to point out.
pink line comes directly from the engine. Should it be coming via the vacuum reservoir?

Pretty sure the diff has a separate vac reservoir in the back of the car

[A80Avant]

also just to point out.
pink line comes directly from the engine. Should it be coming via the vacuum reservoir?

[A80Avant]

vaccum leak found!
which also means that a boost leak is also sorted

[newsh]

Check the little vacuum tubes under the back seat, there’s a one way valve and a T piece with rubber connectors that come off.
I think the engine bay vac line is the pink one, make sure it’s not leaking where it connects to the manifold.
Otherwise if the lock mechanism is getting vacuum then it might just be stuck and need freeing off.
I think you can get to the abs module in vagcom but I’ve never known one to go wrong.

[A80Avant]

I recently checked and my diff lock doesn't work.
Button lights up when pressed and the light was checked and does light up manually(when given appropriate voltage) but when it's supposed to work it doesn't. No ABS light comes up in the dash, and diff doesn't actually lock.

Is the diff ecu accessible through vagcom?

If I check all the appropriate lines, how can I test or make out if this is a diff module issue or something else?

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[malncol]

a bit off topic but what sort of hp will the diff locks take before they let go. looking at rally use ????
mal

[afterburner]

I will take one later that week!

[UrS4boy]

Yep! It was there and I just cut the speedo signal wire Now waiting for the winter

If you take a photo of the B4 controller, I will add it to my rear diff lock post to make it more complete (with credit to you for the photo).

Dave F.

[afterburner]

Based on my friend Kate, she says yes (B4 illustration 919-98) But only one way to tell for sure. Remove the B4 rear seat and look for the silver controller box like this one:

Yep! It was there and I just cut the speedo signal wire Now waiting for the winter

[Zoig]

Zoig: Hmmm.....09/94 = 1995 model year. I *had* understood that EDL (no mechanical lock, just the ABS systems controlling rear wheel spin by applying the brakes to the spinning wheel) was a 1996 model year "feature". When you say you added the mechanical diff lock, what did you add? A complete mechanical diff lock rear differential or ???

Yes, only had the ABS controlled lock system from factory. I added full system from UrS4, all the vac lines to the rear seat, wiring harness (bit modified as explained), the switching box and the diff with lock.
The lock is also not connected to ABS, so i can run with EDL and rear lock if needed.

BTW, my old 1993 80 Avant FWD also had EDL on front wheels, no idea why someone ordered it instead of quattro.

[UrS4boy]

My 09.1994 built UrS6 didn't have the mechanical diff lock, only EDL. Later I added the lock and whilst creating the harness I left the speed signal wire out alltogether.

Zoig: Hmmm.....09/94 = 1995 model year. I *had* understood that EDL (no mechanical lock, just the ABS systems controlling rear wheel spin by applying the brakes to the spinning wheel) was a 1996 model year "feature". When you say you added the mechanical diff lock, what did you add? A complete mechanical diff lock rear differential or ???

[UrS4boy]

Is the diff lock module of the B4 sedans also under the rear seat?

Based on my friend Kate, she says yes (B4 illustration 919-98) But only one way to tell for sure. Remove the B4 rear seat and look for the silver controller box like this one: