Re: Subject: Re: Question: 80Q "limited slip" center diff doesn't limit slip...

["Avram Dorfman" <dorfman@est.org>]

I can offer two comments on this:

1) My brother's '88 80q manual says that his center diff is "... a tor-sen,
or 'torque sensing'..." center differential

2) a full slip center diff w/ a locking rear diff wouldn't make help that
much: the whole point is to make sure that more than one wheel will turn if
you're in a low traction situation. Consider this:

    a) A full slip diff allows one side to spin free while the other side
doesn't move.
    b) the center diff is between axles; if it was full slip, then one axle
could "stop"
        while the other one spun
    c) if you lock *just* your rear diff, then it has twice the traction of
either front wheel
    d) since the front diff is full slip, then if a front wheel is on ice,
the rear axle will
        sit there locked with all it's traction, not moving, while the one
front wheel spins free.
        The full slip center diff would allow this
    e) The reason that early quattros allowed you to lock the center alone,
but not lock
        the rear diff alone is because it is between axles, not wheels.
Locking it guarantees
        that both axles will turn. Thus, even if both front & rear axles
have full slip diffs, you are
        guaranteed that at least 2 wheels will spin, one front and one rear.

Conclusion: Locking an axle diff doesn't guaranty you'll get any more
traction. Locking the driveshaft diff does. Thus, 80q/90qs probably don't
have a full slip diff in the center b/c since they don't let you lock it,
the result would be inferior to the drivetrain in 4kq/5kqs.

disclaimer: I've never been inside these drivetrains. I've been told that
the front diff is integrated into the transmission. I don't know how that
changes things. I assume that the following layout is equivalent to reality
in the analysis above (lck=locking, trsn=TorSen, fs=Full Slip):

(fixed width font)
rrwheel                    rfwheel
   axl                       axl
 lck-diff----trsn-diff----fs-diff
   axl                       axl
lrwheel                    lfwheel

(variable width font)

rrwheel                    rfwheel
   axl                             axl
 lck-diff----trsn-diff----fs-diff
   axl                             axl
lrwheel                    lfwheel

Are there any comments on my analysis?

-Avram


-----Original Message-----
From: Perry, Chris <perryc@wdni.com>
To: 'C1J1Miller@aol.com' <C1J1Miller@aol.com>; quattro@audifans.com
<quattro@audifans.com>
Cc: dorfman@est.org <dorfman@est.org>
Date: Friday, June 18, 1999 4:54 PM
Subject: RE: Subject: Re: Question: 80Q "limited slip" center diff doesn't
limit slip...


>I was always under the impression that the rear diff in my 89 90q was an
>open diff, not a limited slip.  Can anyone verify/disprove this?  I had
>thought this was why they supplied a locking rear diff, because an open
diff
>is UNlimited slip.
>
>chris perry
>
>