Re: Quattro Differentials?

[Luis Marques <marques@rtis.ray.com>]

ti@amb.org (Ti Kan) wrote:
> All Audi quattro models produced to date are full-time all-wheel drive
> (that means power transmitted to all four wheels all the time),
> regardless of diff lock settings.  The differential lock design have
> changed as the quattro system evolved over the years, but that mainly
> affects the car's torque-split characterstics when one or more wheels
> begin to lose traction.  The early locking diffs cause a fixed 50/50
> torque split to be enforced under all conditions, whereas the later
> t*rsen diffs provide dynamic torque transfer characterstics.

A small clarification point to Ti's great reminder post - the early
locking diffs have a fixed 50/50 torque split when _unlocked_ (just as
any other open diff).  In this case if one wheel has no traction, the
other gets no power and you don't move.  When locked however, the early
diffs force both ends to turn at the same speed and in the process
provide 0-100% power split depending on which end has the most traction
and can get you out of almost all sticky situations.  

T*rsens simply don't lock.  They actively distribute torque up to a
~20/80% limit.  This means that the wheel with more traction gets up to
fourt times the power as the wheel with less traction, but if that wheel
has no traction, zero times four is still zero ;)  Under normal driving
conditions, ALL quattros send 1/4 of the power to each wheel.

Luis Marques
'87 4kcsq