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[Paul.Heneghan@bbc.co.uk (Heneghan,Paul)]

>From: "John W. Seitz" <jwseitz@SNET.Net>
>Date: Sun, 26 May 1996 23:33:51 -0400
>Subject: 4000CS-quattro vs. The Gas Pump
>
>If I switched on the =
>center diff (mode one) it would help quite a bit but my dealer says That =
>should not be used ???  In mode2 all locked its like a tank!!  Can that =
>dail in the center console be used and when and is it normal for a AWD =
>to handle that way?? 

I have the owners manual for my 1984 80 quattro (same as a US 4000CSQ). 
  It has a section on when to lock the centre diff. which recommends 
 locking it under the following conditions:
	high-speed driving
	wet or slippery conditions (obviously including snow)
	car fully loaded
	car pulling trailer
Do not lock it in town conditions where frequently turning corners will 
 scrub all the rubber off the tyres.  You can feel if it is locked 
 inappropriately - the car will judder when going round corners.  I 
 usually lock the centre diff. when travelling at speed down country 
 lanes - the cornering is like the car is on rails (it doesn't stop you 
 spinning the car if you exceed your or the car's capabilities - I came 
 to rest having spun 180degrees with the indicator lens cracked by a 
 signpost warning about bends on the road!)

I believe Audi's race quattros used to do away with the centre diff completely.

In addition, the rear diff. should be locked whenever you are 
 struggling for grip, e.g. if you are stuck in a muddy field, or in a 
 snow drift.  It should be unlocked as soon as you have got going 
 (again to avoid excessive tyre wear and unusual handling).

The dealer is speaking out of his nether regions if he says the diffs 
 should never be locked - why are they there in that case?

Paul
paul.heneghan@bbc.co.uk