[torsen] Re: [s-cars] Torsens is there a difference ??!!

QSHIPQ at aol.com QSHIPQ at aol.com
Tue Dec 3 11:40:35 EST 2002

Rob et. al.:
I'm not really convinced that this is good information, I suppose it could 
be, but I doubt it.  The S cars use the "university special" known as the 
M021-DHU, it's basically the same unit audi used from 1988>.  As far as I can 
tell, they are all the same, AND the ways to modify them would be steel shims 
and/or changing friction within the unit.  I'm suspect of the 75% torque vs 
80% torque, cuz really we are looking at a 5% torque differential here 
(assuming all cars are equal in terms of torsens, they aren't, they wear 
immediately and stabilize at something much less than the 3.5TBR).  If you 
math this out, we are speaking of less than 50ft/lbs of torque, I doubt 
that's at all significant.

751E shows valid for the 5 or 6 speed variants of all 01E based 
transmissions.  AND this is the "university special" based basket, which 
means that the differences might be getting TO the unit or coming FROM the 
unit in terms of splines/size/fitment but the unit itself hasn't changed.  
Even torsen admits that .7TBR variation *should* be expected as delivered for 
the "new" university special.  I can't imagine that the "old" one could 
possibly be better.

I'm most intrigued by the infomation that comes from all different sources, 
including zexel torsen themselves.  Audi started a fine tradition of 
mystifying this basket of spiders.  I really doubt it's ever been this 

Rob, Stasis did some data logging of the driveshaft speeds on the torsen in 
their race car, it's interesting reading, even if the conclusions might be a 
bit off (IMO).

Right now, I will put forth that the 78% vs 75% vs 80%  (this is the first 
time I've seen 80% on a center diff referenced, I've seen it as the rear v8 
torsen) is well within the production tolerance of the device, and "seeking" 
one over the other isn't time or money well spent.  Audi has published 75 and 
78% for all 01E based trans (in my library anyway), I wholy consider those to 
be both valid, since when new either number could be, when used, neither 
number is.


Scott Justusson

In a message dated 12/2/02 12:09:53 PM Central Standard Time, rbraun at foni.net 

Hi Peter:

Our conversation got me really curious and so I decided to poke around a bit. 
The most detailed information is in German and after reading about 10 
webpages and speaking with Mr. Kluge here is the final word on Torsens:

ALL Torsens split the torque 50/50 all the time. There is no difference here.

There are only 2 Euro versions of the Torsen: 01E 409 751 and 751E. The 
difference is in the MAXIMUM torque split under conditions where the Torsen 
has to divide the torque (read: wheel slippage).

The 751 splits the torque up to 80% to one axle. It is installed in ALL V8 
transmissions and the CRB.

The 751E splits the torque up to 75% to one axle and is installed in all 
other Quattro transmissions, even the new TDI ones and the S2.

The reason Audi changed the torque split for later models was twofold: one to 
prevent too much torque from going to one axle and causing damage. The higher 
torque split also has more torque shock under those conditions with all 4 
wheels spinning and so Audi lowered the torque split to keep the peak torque 
load and resulting shock within limits.

The average driver won't notice the difference.

Hope this helps.

Kind Regards


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