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what's under all that pretty paint (Q & diffs 'n stuff)



re: differentials and the basics of what a quattro is:

Quattro is a fully mechanical, full-time all wheel
drive system.  All four wheels are driven at all times.
Under normal circumstances, they are all free to turn
at different rates, so that friction and tire wear
are small, and steering is smooth.

This requires three differentials:

1) front=> normal diff, cannot be locked, allows free steering
2) rear differential => noral type, can be locked below 15 mph
3) center => between the freont and rear diffs (part of trans case)

The center differential is the torsen.  It differentiates
power in proportion to traction (torque) rather than motion.
This means that when a wheel spins on a noral car/diff, all
the power goes there, and (a) you don't go, and (b) you
fishtail (or plow if FWD).

If power is sent to the wheel that grips, rather than slips :-),
then you get better forward motion, and less tendency to
fishtail - but Qs still do anyway.

There's some disagreement over the mecanism of a torsen.
I remember an article by the company that holds the patents
(Gleason Works - New York) discussing the linear torque
and motion split mechanism.  Someone (forgot who-sorry)
claimed that it was an auto lock at various mixes.

If its fast enough, I guess we're in the old digital audio
quantizing noise arguaments here :-)  If its a small number
of steps, then I hold that its a linear differential.

Wind off. Its safe to look at the email again.

Grant