Quattro generations (was: Miata Torsen)

[isham-research.freeserve.co.uk at pop.pol.net.uk]

> 1. circa 1982-88 "quattro I"
>    - Front open diff
>    - Center open diff with vacuum operated manual lock
>    - Rear open diff with vacuum operated manual lock

>    This system is not ABS-friendly because locking the diffs effectively
>    eliminates any speed difference between wheels, disabling ABS wheel
>    speed sensor function.  On the 5K/100/200 models that has ABS, it is
>    automatically disabled when a diff lock is activated.
>    Used on 1982-85 UrQ, 84-87 4Kq, 86-88 5Kq/100q/200q

I don't see that it's that ABS-unfriendly.  The rear wheels share an
output channel in that system and are released/braked as a pair anyway,
diff locked or not.  Besides, only a fraction of the braking effort
comes from the rear.

> 2. circa 1988-95 "quattro II"
>    - Front open diff
>    - Center Torsen diff
>    - Rear open diff with vacuum operated manual lock

>    The rear diff lock will auto-disengage at >15mph, so the system is
>    ABS-compatible.
>    Used on 1988-94 80q/90q/CoupeQ, 100q/200q

Also 1988-91 ur-quattro.  There's also some confusion about the rear
differential - quite a bit of Audi's documentation refers to the ALZ
as a 'limited-slip differential'.  See ETKA AQS/88/5/25/45-30, for
instance, and the service microfiche.  I can't see _anything_ in the
construction of the ALZ to justify this claim.

--
 Phil Payne
 http://www.isham-research.freeserve.co.uk/quattro
 Phone +44 7785 302803   Fax: +44 7785 309674