more center differential stuff.

[dmichael@tdh.qntm.com]

There have been a few posts, and I have received a few messages regarding my
posting asking if anyone had any experiance with a non-locking TORSEN
center diff. There was also a question about how the quattro system works.

Evidently, there is some confusion out there about the differences bewteen the
two generations of quattro systems, since several people have suggested that 
I lock my center diff "using the switch".  That is not possible, since there 
is NO manual lock for the Torsen center diff. 

The first generation Quattro system has THREE conventional differantials.
One between the front wheels, one between the rear wheels, and one 
between the front diff and rear diff. Each of these works like normal,
everyday differential - Which means if one wheel has no traction, ALL the
power goes to that wheel. Your FOUR wheel drive car becomes ONE
wheel drive. That is exactly the same as any plain old  2wd drive car with a 
normal diff. Except Audi knew this, and gave you the possibility of manually 
locking the center and rear diff (either just the center, or both). With
both center and rear diff locked you then have a THREE wheel drive car, since 
you need to have BOTH rear wheels and ONE front wheel spinning before you 
stop moving.

The second generation Quattro system replaces the manually locking center 
diff with something called a TORSEN (TORque SENsing) differential.
These diffs, insead of having the bevel or spur gears of a normal diff., have
worm gears. With the correct pitch, the "worm" can turn the "worm gear",
but not vica-versa. The is SUPPOSED to give the diff magical abilities
to sense where the torque can MOST be used, and send the torque in that
direction (up to 75%, the owners manual states). Cars with the Torsen center 
diff still have a manually locking rear diff. 

The problem I had was that the Torsen didn't seem to do its job. It sent all 
the power to the end of the car that could LEAST use it, just as a regular
diff does.  So as far as I am concerned, Audi replaced a system that worked
fine (manually locking diffs), with one that makes the whole quattro system
much less effective. The really deceptive thing is that the owner manual
stated that the diff "automatically locks", which, from my experiance,
is simply not true.

I have not yet taken the car to the dealer, but in general, they have been
friendly, cooperative and not very knowledgable about Audis (Audi is their
Emergency-Back-Up, Auxilliary Car Line).

Hope that clears things up,

Dave