Re: Diff locking question ...

[paul.heneghan@bbc.co.uk (Paul Heneghan)]

From: steveb@falcon.kla.com (Steven Buchholz)

>I found that when I lock the center diff the car is
>difficult to move and it appears that stress builds up in the drive line
>as the center diff will not unlock until you reverse direction.

I had this on my 80q.  If you had the centre diff locked and coasted to a 
halt, the car would slow down and stop quite quickly (even with the steering 
in the straight ahead position).  I put this down to slightly different 
radius tyres - I imagine even a couple of millimeters of difference would 
significantly increase the rolling resistance when the car is in neutral. 
 When accelerating, this increased friction would then be negligable in 
comparison to the huge amounts of power/torque being generated.

I also had to drive the car in reverse for a few meters to get the centre 
diff to unlock.  When checked on a car hoist, everything checked out OK, but 
on the road it was very unwilling to unlock.  Putting the car into 2nd gear 
and trying some savage accelerations and decellerations would often do the 
trick (to the accompaniment of clouds of smoke from the exhaust).

Last year I changed my rear diff mounts.  To my surprise, the centre diff 
then unlocked with ease - I can only assume that the sag in the rear diff 
was causing stress in the Bowden cable and causing it to partially seize up 
(sorry about split inf.).

YMMV

Paul
paul.heneghan@bbc.co.uk
1984 Audi 80 quattro
1989 Audi 100 Avant