4wd vs awd

[Larry C Leung]

The center diff locks were removed and replaced with a Torsen center diff
to accomodate ABS in even high slip conditions. The rear diff through
mid-nineties was still manually lockable, but it auto-disengaged at about
15 MPH (25 kph). The exception was the V8 model which (at least in the
auto tranny models) had a Torsen rear diff as well as center diff. The
latest quattro system uses what amounts to traction control via the ABS
sensors to emulate a diff locks.

LL - NY

On Fri, 27 Apr 2001 10:54:02 -0400 "ricematthews at msn.com"
<ricematthews at email.msn.com> writes:
>>Does that mean cars like the LandCruiser are actually considered to 
>be all
>>wheel drive?
>
>Yep.  And I believe they are badged as such.
>
>Actual 4WD vehicles generally apply power to the front and rear
>differentials via a transfer case mounted to the back of the 
>transmission.
>The transfer case turns the front and rear drive shafts at the same 
>speed.
>This can be a problem on dry pavement because wheels need the ability 
>to
>turn at different speeds to accommodate turns, and changes in road 
>surface,
>etc.
>
>AWD systems generally use a center differential in place of a transfer 
>case.
>As its name implies, the center diff will allow the front and rear 
>axles to
>turn at different speeds to accommodate turns, etc. and therefore may 
>be
>used full time.  The earlier Audis (like my '86 4KCSQ) have the 
>ability to
>lock both the center and rear diffs for times when the going gets 
>really
>slippery.  This makes it similar to 4WD.  Audi apparently discontinued 
>the
>center diff lock by the time my '89 200Q was built.  I can only assume 
>that
>too many people were leaving the thing locked on dry pavement causing 
>the
>center diffs to self destruct.
>
>Would any of you know - are the center diffs on the later models 
>limited
>slip - to compensate for the lack of a lock feature?
>
>
>