4kq diff lock switch explanation?

[Dave Hord]

Hey all,

My patient is my 1989 Audi 90 quattro, being converted to a rally car.

My rear diff lock controller died. Not really a problem as I wanted to go to
manual control anyways. The 90q rear diff works in the following manner:
there are three lines - Vac from the engine, one line to lock, and one line to
unlock.  When you push the diff lock button, the electronic controller
connects the vac line to the 'lock' line. When you push to unlock, it switches
the vac line from the 'lock' to 'unlock' line.

I have pulled a diff lock switch from a 4000q to mount in my 89 90 quattro.
The 4000 quattro diff lock switch I have is part number: 857 711 981A
The 4kq switch has five vacuum lines going in/out of it. Going from the knob
(dashboard) to the end (firewall) the vacuum line colours are as follows:
Yellow/Green/Unknown/Red/Dark Blue.

Silly drawing follows:
      __
     /  \
     |  |
     |  -----------------------------
     |                               |
     |  ---| |--| |--| |--| |--| |---
     |  |   Y    G    ?    R    B
     \__/


Can anyone tell me what the above lines are for?

I realize that some of the lines are for the center diff, and some are for the
rear diff.  I will plug the lines that I don't need (90q has no lockable
center diff...Torsen)



I want to connect the switch as follows:

Pull the switch all the way out of the dash: Rear diff locks
Push the switch all the way into the dash: Rear diff unlocks

This will allow me to just yank the knob out of the dash to lock the diff, and
slam it back in when I want it unlocked. Makes it pretty 'brainless' to use.

I haven't had the opportunity to play with the 90q rear diff much, but I
suspect that it can only be locked while the car is not moving...but can be
unlocked at anytime.

Can anyone confirm if I can lock the diff while it is motion?

TIA

-Dave


--------------------------------------------------
89 90q  300km+ Rally Conversion in High Gear...
(sometimes it helps to hit trees??)
http://home.the-wire.com/~spokes