[s-cars] Quattro - What Don't I get?

[calvinlc at earthlink.net]

A couple of questions for you Quattro gurus.  I did an experiment today with
my S4 and then repeated with my '89 200.

I put both right side tires on ice and the left sides were on pretty good
pavement.  I dropped the clutch and both right side tires spun like hell
while the left sides barely turned (both cars result in same).  Is this
because there is no torque being applied to the spinning wheels and
therefore the non-spinning wheels don't get much torque either (i.e. open
diff with a 50/50 torque split)?  I would guess this is why EDL works
nicely, right?  BTW, is the EDL system on the newer A6's pretty much the
same as what was offered in the UrS6?

I then reversed it so the left sides were on the ice and both left sides
spun and both right sides barely turned (same on both cars).

I then tried the same thing with the diff lock on.  This resulted in no
difference with the S4 but a good bit of difference with the 200, i.e. rear
wheel on dry pavement caught pretty good.  I would guess this means my diff
lock in the S4 isn't working.  The light comes on and goes off at anything
over 15 but the rear diff doesn't appear to be locked.  Are there any common
items that would make this happen?

On a side note since we are talking about differentials; does anybody know
why it is that every open differential RWD car I have ever owned spins the
right side tire when the clutch is dropped and never spins the left side
tire?  I would think some would be more predisposed to left side spinning
and some more to right...what's up with this.

Thanks for your help!

--Calvin