4wd vs awd

[ricematthews at msn.com]

>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?