[s-cars] Wiring "upgrade" for torsen rear diff users

[Kirby Smith]

OK, you have installed a torsen rear differential and have decided its a
keeper.  The following describes a chenge I made to my differential lock
wiring for my convenience.  While it specifically applies to a 1995 S6,
I suspect the earlier cars are very similar.

Remove rear seat bottom.  (Now is a good time to check your battery
fluid levels.)

Note that roughly in the center of the car is a module with three vacuum
hoses attached.  This is the rear diff control module.  Attached to its
mounting bracket is a gray connector.  Note that two wires go into the
connector, and three leave it.  The two-wire side connects to the switch
on the differential itself via a connector that you or your mechanic may
have pulled up into the rear seat area to keep it clean.

The other side of the connector has one brown wire (goes to chassis) and
two brown-swartz (black) wires.  One of these wires, when grounded,
turns on the green light on the differential status indicator.  My goal
was to keep it on, indicating permanent "lock."

The other wire disables ABS when grounded.

Cut the three wires from the connector and strip them back a quarter
inch.  (Removing the sockets from the connector is possible with a
Snap-on German connector tool set, but not particularly useful.)  Using
clip leads, determine by experiment with the car running which
brown-black wire, when connected to the brown wire, turns on the green
light.  The other turns on the ABS light in the instrument cluster. 
Shut down the car.  Connect the brown wire and green light enabling
brown-black wire using the connector scheme of your preference.

Would you like a simple ABS switch using the now unneeded differential
lock switch?  For negligible further cost, attach an over-wire splice
with a flying lead onto the brown-gelb (yellow) wire connected to pin
4/L of the differenctial control module.  Connect the other end of the
flying lead to the remaining brown-black wire from the gray connector
using the connection scheme of your choice.  Now, when the differential
lock switch is pressed, the Anti-Lock light will illuminate in the dash,
and the ABS will be disconnected.  (That is, presumably, I haven't
proved it at the brakes yet, and with SO-2 tires, may have to wait for
winter.)  Also, I haven't yet disconnected the speedometer wire from the
module.  I expect from the circuit diagram and normal functionality that
the ABS will be reconnected after I speed up past 15 mph or
thereabouts.  I haven't yet decided whether to keep this safety feature
or not.

Relative to the Bentley, the reference schematic is X909.  At trace 40
is a hanging lead indicating it connects to something on trace 34.  That
is the ABS control line.  This line is clipped where it connects to the
T2q/2 connector and instead routed to 4/L on J187 as noted above.  The
other brown to brown-black connection described above jumpers the
differential switch, F100, between T2q/1 and T2q/2.

The time it took to do this was considerably shorter than the time I
spent condsidering the schematic and messing with the gray connector to
see if its internal wire splice was reversible.

kirby