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

[Zoig]

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. Just to be sure I created extra warning lamp in the cluster, it is wired in paralell to the green lamp. I located the warning lamp under the "ASR" (now called "Automated System Recovery" when i get stuck )

Testing of the harness, the cluster warning light is in the background.

[afterburner]

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

[speeding-g60]

also check what happens when you launch >600 AWHP car with the diff not ENTIRELY engaged. i run mine permanently locked all the time, with the center diff locked (welded) as well. this was not fun as we had to get the car on 4 wheel dollies to tow it off the track

[UrS4boy]

NP. I figured The Librarian must have missed those.

Why yes he did. As soon as I get up from the computer I will spin around and kick is @ss.

Added this:

"Here are some great Shift Lock Coupling photos courtesy of 4WheelDrifter on this forum:

Unlocked Position (from the front of the car looking to the back):



Locked Position(from the front of the car looking to the back):


"

[4WheelDrifter]

NP. I figured The Librarian must have missed those.

[UrS4boy]

Also check this.

Thanks for that. Consider those photos "stolen" (by me) with credit given to you as 4WheelDrifter. Soon to be part of the post.

[UrS4boy]

this pics are for the c4 chassi( fits also chassi 44...) but the pics are not for the s2/rs2, but the diff internals are the same as in audi 80/90/s2/rs2; only the diff housing are not like the small chassis. tanks for the nice pics and leads info...!! i have a 97 s6 vagon with 2,2liter too.

The post is trying to focus on the general mechanism of the lockable rear diff. I have to work from my data base which is primarily C4 UrS based.

And you're welcome.

[4WheelDrifter]

Also check this.

[caterpillar]

this pics are for the c4 chassi( fits also chassi 44...) but the pics are not for the s2/rs2, but the diff internals are the same as in audi 80/90/s2/rs2; only the diff housing are not like the small chassi.
tanks for the nice pics and leads info...!!
i have a 97 s6 vagon with 2,2liter too.

[UrS4boy]

I have combined the photos from Yodasfro and Andy10v into this new info:

"Here is an attempt to show how Items 16, 20 and 21 schematically work together(obviously Item 20 would have to be installed at the same time as Item 16 is installed into the differential housing gear set):"

[UrS4boy]

Looking for a photo of the diff lock shift coupling

Item 20 in the diagram below. Out of the differential please. Also the Item 13 selector fork, if possible.

[UrS4boy]

To make engagement easier?

As I understand it, the shift coupling (item 20) is normally parked fully over the teeth on the left rear drive flange (Item 16). When the lock acutator pushes the Item 13 shift fork away from the centreline of the vehicle, the shift fork pivots, pulling the Item 20 shift coupling partially off the teeth on the Item 16 flange and onto the teeth of Item 21, the shift gear that is attached to the rear differential and thereby, locking the left drive flange to the rear differential housing, over-riding the internal rear differential gears, locking the two rear drive flanges (and axels) together. No limited slip clutches here folks, this is the real deal: locked rear diff (albeit, temporary and controlled).

None of this explains why the teeth on the Item 16 drive flange have those shorter teeth sections. Must help the engagement/disengagement.

[andy10v]

Got one:

Note the non-uniformity of the length of the gear teeth in some sections:
(Austin)

To make engagement easier?

[UrS4boy]

from a locking rear diff.

Got one:

Here is the Item 16 left rear flange shaft with the integral diff lock gear. Note the non-uniformity of the length of the gear teeth in some sections:


Base photo courtesy of Yodasfro(Austin)

[UrS4boy]

Looking for a photo of the left rear drive flange

from a locking rear diff. Item 16 in this diagram: