RE: Locking the differential ?

[Aleksander Mierzwa <alex@matrix.com.pl>]

You can't lock the front differential on a quattro, the first position
locks the center diff and the second locks both center and rear.
An ordinary differential has an annoying feature: it transfers the
torque to the wheel with less grip. On a 2wd car if you have one wheel
on the dry surface and the other one on the ice, the one on the ice will
spin and the one on the dry surface won't be driven (fortunately, the
internal friction in the diff allows some torque to be transmitted to
this wheel, too). Although a quattro has four wheels driven, the same
situation occurs. The purpose of differential locks is to ensure equal
50/50 torque split between wheels (or axles in the case of the center
diff). If you happen to have the rear wheels on slippery surface, but
front wheels have grip, yet the rears slip and the car doesn't move,
lock the center diff and 50% of the torque will go to the fronts.
Locking the rear diff is recommended in really slippery conditions. Diff
locks are useless on dry surface (they are sometimes used in competitive
driving to alter the handling, though).

Aleksander Mierzwa
Warsaw, Poland
mailto:alex@matrix.com.pl
87 Audi 5000CS turbo (mine)
88 Renault Medallion wagon (mom's)
91 mountain bike (just in case both cars broke at the same time :-)

> -----Original Message-----
> From:	ARPCAxPREZ@aol.com [SMTP:ARPCAxPREZ@aol.com]
> Sent:	Wednesday, October 29, 1997 4:44 PM
> To:	quattro@coimbra.ans.net
> Subject:	Locking the differential ?
> 
> I'm a little confused on the application of locking the
> differential..............I have a ' 87 5KsQ and on the dash there is
> a 2
> postion differential switch.  Turning the switch to the first position
> locks
> the front differential, and turning to the second position locks the
> rear
> differential..............Does this mean...............if I run the
> rear of
> the car off the road -- we'll say the rear end slid out onto a snowy
> shoulder
> slope as we were rounding a turn -- Now...... do I lock the
> differential to
> the front ? ......so the front wheels take all the power to pull the
> car out
> ?   Is this the purpose of the locking differential ?   Also when
> locking the
> differential.......does it have to be a slippery roadway or could it
> be dry ?
>  and  do you need to keep your speed down  or  could you drive at a
> normal
> speed ?    Thanks for the advice
> Sincerely,
> Bradley Blumfeldt
> Pittsburgh PA
> ' 87 5KsQ  plate: X X X X