[torsen] Re: front locking diff - TB late into the game here...

QSHIPQ at aol.com QSHIPQ at aol.com
Mon Dec 27 11:34:15 EST 2004

Torsen Boy arrives late:
Keith has the operation correct, the v8 (Auto only - manuals used torsen center)is all wheel drive, with a lockup center based on ABS sensor input.  The rear on v8's (all) is torsen.   The  front is open.  It should be, turning radius will get downright ugly, and tire wear would be unruly.  Even Audisport  WRC (80's) rally efforts used in FRONT:  20% locker (VC type), fully locked (no switches, all diffs were locked in this config), or open (with locked center, LSD rear).  Front config was driver preference, and most preferred open or all locked.  The 20vt cars tended to go open front (with locked center, 80% LSD -clutch type rear), then as power increased, the trend went back to locking them all.

I have many miles on a Group A S2 SMS/MTM Rally car (fully locked F/C/R), and I can tell you that driving a locked front is high stress anywhere but in loose dirt or snow.  The biggest problem with any type of LSD in front is the massive understeer it provides (not to mention the heat it generates).  Turn in on pavement is next to improssible, and turn in under power on pavement is unpredictable (btdt).  

I just returned from the xmas holiday with our '91 v8auto, 5 solid days of snow covered roads.  As most probably know, those conditions are my forte (see www.gruppe-q.com).  I put on some handy 195/65 Pirelli Winter 210's (non ice) on 15x7 in wheels, and put the v8 thru it's paces.  With chip and intake mods, I could literally floor the car in sport mode, with nary a hint of sidestep.  In fact, many a sport ute found the sure footedness of our machine very overwhelming, especially on the back roads.  

My conclusion?  I don't think there is a better quattro system than this autobox with it's locked center with a torsen rear, open front.  If you are really into rallycross or snow, the rear locker has a happier tail (what I run at Steamboat with the urq).  But short of full rallycross regalia, the v8 locked center torsen rear has few equals in terms of sheer traction.  With a flat torque/hp curve, autobox and seemless interaction of the center diff, I doubt I'd beat our v8 with any of my turbo quattro cars, it's that darn good.

Summary:  Forget LSD in the front of a quattro.  Your money is much better spent on training and condition specific tires.  You already have the best of the early EDL cars Audi made.

WRT locked fronts in trucks:  Non military would include Landcruiser (optional), g-wagon (military based I guess).  IME with trucks ('87 4runner turbo off roader), the best setup for the winning off road (crawling competition) is a locked center, locked rear, and front torsen with lockout hubs.  The nice thing about this setup is that when you disconnect the lockout hubs, the torsen becomes inactive.  

Best to all for the Holiday Season

Scott Justusson
'91 v8
'84 RS2URQ project
'83 Urq
'87 4Runner turbo

In a message dated 12/21/2004 4:03:01 PM Eastern Standard Time, dsaad at icehouse.net writes:

>Are you sure about front diff locking?
>I am not aware of any non-military vehicle with a locking front diff.
>(of course I am not aware of a lot of stuff :-)
>Lots of people put them in themselfs, but this is usually the hard core off road
>types. All of these 4WDs (owned by me) - 1988 Bronco 2, 1983 Ranger, 1993
>Explorer, had severe driveline lockup problems if you tried to turn on dry
>ground in 4WD. The front end would hop up and down.
>These vehicles did not do that - 1971 Jeepster Commando, 1998 Explorer, 1999
>They ALL had open front diffs, and the Explorers and Expedition all had locking
>rear diffs. The difference is the old Jeepster and new Fords have constant
>velocity joints at the front hubs.
>With that you can actually do a U turn on dry pavement with a lot less driveline
>twist up. It is still really hard on it though.
>Quoting Michael Larosa Jr <Mc.Larosa at Sun.COM>:
>> exactly,  my trucks front diff locks up tight,  can't drive it
>> this way unless road is covered with snow..
>> but the rear is limited slip..
>> Carter Johnson wrote:
>> > As Steve et al said, non of the early cars have
>> > locking front diffs.  If they did, you wouldn't be
>> > able to turn.  If you did turn, you'd break something
>> > (A la rear locked diff, 4000 Quattro, dry conditions.
>> > Watch the back jump in turns.)
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