Locking torsens?

[Lawrence C Leung]

Any Quattro (not including the TT) is full time all wheel drive, which
means that approximately 50% of the torque is directed to one front axle,
the other 50% is directed to one rear axle. Any non-limited slip front or
rear drive car has approximately 100% of it's torque directed to one of
the two driven axles at the end of the car that is driven. Hence the
quattro system has an even distribution between front and rear axles and
at least two driven wheels at one time (vs one driven wheel for FWD or
RWD).

The purpose of the locks is to guarantee the front rear distribution. For
quattro 1 (pre-89 type 44's, pre type 89 (80-90) smaller body Audi's),
this is accomplished by a true mechanical locking mechanism, as the
center diffy is an open diff, so in extreme situations, it is possible to
one wheel drive even a Q1 without the lock. In later quattros, (excluding
your V8Q) it's accomplished with a viscous coupling called T_rs_n, which
"senses" slip at one end a redirects torque to the other end up to a (I
think, list may correct the %ages) 30-70% or 70-30% split. The use of the
T_rs_n allowed for the use of ABS while maintaining driven axle control.
The rear of these later Q's have an electronically activated mechanical
lock to lock the rear driven wheels together for extra slippery
conditions. This is driver activated.  This system unlocks at 15 MPH, b/c
if you can go that fast, you don't need to have a locked rear. In the
case of either version of Q, the general idea is that the rear diffy is
locked ONLY to break a stuck car free, it's not recommended to drive the
car at higher speeds with it locked, as the lack of differential action
may cause the rear end to break free on turns. In either case,  AT NO
TIME can you turn quattro OFF. The drivetrain will ALWAYS attempt to
drive both ends of the car. 

As for your V8Q auto, there is a slightly different function (V8 owners,
or V8listers help). AFAIK, the center diffy of the autobox V8Q's has an
electronic center lock that senses slip via the ABS sensors, and a T_rs_n
rear diffy lock, making the entire system automatic at all times. There
is no decision making for the driver to do. Again, both the front and
rear axles of the car are (attempted to be) driven at all times, and
again there are no factory controls designed so that the car could be
made an on demand FWD car. 

LL - NY 

On Wed, 13 Dec 2000 07:23:24 -0500 "Theron J. Bliss" <tbliss at mestek.com>
writes:
---------snip---------
>didn't bother buying the quattro and she said that the dealer told her 
>the switch
>was so you can turn off the quattro.  He said it should only be used 
>in deep snow
>and below 15 mph, or it could ruin the car, and that beyond that, the 
>quattro was
>useless (her husband was also convinced of this).  Now I knew he was 
>full of it,
>just trying to sell a car that was probably sitting on his lot a 
>while.  But I was
>told later that the switch doesn't turn off the quattro, but mearly 
>lock the
>differential.  My question then is, can you use that switch on any US 
>Audi
>Quattro, to make it 2 wheel drive?  I'd love to show them that he 
>wasn't on their
>side.  After all, it had about 70k miles on it (purchased last 
>winter), and was a
>1993 100 fwd, leather, no climate control, and they paid around 
>$17,000.  Can
>anyone say highway robbery?
>
>-Theron
>
>