I could swear that I've seen a nice drawing that illustrates how the differential locks vacuum system works for 5000 Quattros . . . but I can't recall where.

I've not found it in either the Haynes or the Bentley shop manuals.

I'd also like to see photos or drawings that illustrate where the differential lock vacuum servos are located. The very last page of my Bentley manual has a drawing of the transmission case that illustrates the servo for the center differential lock on the passenger side of the transmission case (I guess just above the catalytic converter).

My reason for asking is that neither differential lock on my 1988 5000CSTQ works and I'd like to repair this problem within a few weeks. Since neither works I'm guessing that the fault has a common cause, such as the vacuum system that powers the diff locks.


TIA.

there are two lines and a electrical sensor on the pass side rear of the diff.
If you lift your rear seat out you can see the two vacuum tubes ... I think one has a yellow strip and one is blue. If you suck on this it should move the actuator at the diff one direction .... if you do the same with the other one it will go in the opposite direction ... hope this helps.