Quattro IV ...???

[TM]

Michael,
Much has been said about this in the past, but briefly:

I: open diffs, lockable center and rear via vacuum actuation (UrQ,
4kq, VW QSW, 5kq/tq)

II: Torsen center diff, open rear, lockable rear via vacuum actuation
(80/90q, 100/200q, C4 100q, UrS (except '95.5+))

III: ?? This could be the V8q- Torsen center and rear, I think?

IV: Torsen center diff, open rear, Electronic Differential Lock (fancy
name for a traction-control system on the rear axle using the ABS
sensors and the brakes to equalize the rear wheels) (A4, A6, A8, '95.5+
UrS, S4tt, S6, S8)

V: Haldex AWD- electronically actuated differentials? (A4 chassis VWs
and the TTq)

I'm certain I've made some errors on this post- I know some listers will
make whatever corrections are necessary. :-)

As for how the system works, Audiworld has a nice FAQ, I think it's in
their
technical section.

BTW- S4tts _DO NOT_ have dual Torsen diffs.

Taka