Re: Locked differential driving

[edudley@mailbox.syr.edu]

                              SNOW/ICE driving
> 
> So... How can you steer on snow with the rear diff locked?  I don't autocross
> at all, but when I lock both diffs in snow/ice, it's really difficult to
> steer. I don't think locking the rear diff is a good on_road technique
>  (is it)?
> Am I missing something?
> 
>           Well, I drive with a tail-out rally type style. With just
>           the rear diff locked, I start the turn with the wheel and
>           then control and complete the turn by steering with the
>           throttle. By modulating the throttle I control the amount
>           of rear-wheel wheelspin and hence the radius of the turn.
>           This is NOT for the novice and should not be used in
>           traffic, etc.

I find the 4000's respond well to toe adjustments.  Cursed understeer
can be nearly eliminated with front and rear adjusted to the minimum
toe-in (maximum toe-out) spec.  It can be completely eliminated in the
region beyond the spec, but the effect gets non-linear real fast and
finding the right adjustment can take a while.  Furthermore the effect
is more pronounced as the ball joints and tierod ends wear, so the car
get hairier and hairier, need adjustment, gets hairier, and so on,
whereas a good stock adjustment can often last the life of the components.

The other thing would be to have some tires that will bite enough to
initiate the turn.  With poor to average tires and diffs locked the
car sure seems like all it will do is go straight.  You can usually 
equalize the rear slip angle with an agressive chop of the throttle
as the wheel is turned just enough to use all the turning traction,
or even lie to the car and suggest that you're going to turn left by
throwing some weight to the right, the chop throttle and turn the
car when the weight lands back on the left.  The bad news is that
either of these works better the faster you're going, which is
hardly what you want for nice full control goofing around.

With decent tires it's a whole different story.  You can set the attitude
of the car under braking (thanks to the locked-diff=no-locked-wheels
phenomenon somebody mentioned) or with trailing throttle and then 
throttle steer the car very easily.


> 
>           I've got my Winter Beater (Tm) '84 4000Q setup so that
>           I can lock just the center diff, or just the rear diff.
>           Rear diff only is definitely the HOT SETUP for rally-
>           style hang-the-rear-out-at-WFO-style turns. *EXCELLENT*
>           in the snow and ice where these cars have so much #$%@#!#
>           traction that they can actually be boring. :)            
> 
>           Rear diff only locked + snow = boring !NOT!

The center diff mechanism stopped working on my 84 4000Sq Winter Rat
one day and the thing performed vershit.  When driving meets stopwatch
power induced oversteer is relegated to Starskey and Hutch chase scenes.


   Eliot