[torsen] Re: 89 centre differential

QSHIPQ at aol.com QSHIPQ at aol.com
Fri Dec 14 09:01:02 EST 2001

> Can anybody shed light on the center diffs of my car's vintage.  For example
>is it open or limited slip?  Can I retrofit a locker easily to the center
>diff? Does it bias power to the front greatly?  Is it correct to assume that
>this is even my problem??  Is it viscous or torsen?? etc...

Phil Payne writes
>>It's a TORSEN.  Key things are:

>>a) Four-wheel alignment must be close to perfect.  'Within tolerance' is 
not good >>enough - you may have to do some POWERFUL
>>insisting to get it set exactly right.

Phil, could you help us with the definition of exactly right?  I thought that 
was 'within' tolerance by definition.  I've also been witness to many 
alignments where just the raise and lower of the alignment bed causes exactly 
right to vary.  A better term might be, as close to mid range in all 

>>b) A TORSEN distributes torque - it must therefore have some in order to 
work its >>magic.  On a trailing throttle or when braking,
>>it's just a heavy piece of metal.

That's not true according to the torsen literature.  ANY torque applied to a 
torsen needs to be distributed.  That would mean by definition, acceleration 
and deceleration.  It "could" be argued as not significant, unless you lift 
mid turn with 78% f/r torque distribution.

>>TORSEN technique is to enter a bend slowly and go round it under power - it 
>>doesn't have to be much.

When it is "much" it can be a problem.  The only shortcoming of torsen I can 
see, is that it distributes torque on power based on traction OR turning 
radius, because the device can't tell the difference between the two.

For more on the audi application of torsen, get these two papers from SAE:
C368/88 = The development of a differential for the improvement of traction 
885140 = The influence of a torsen center differential of the handling of 
four wheel drive vehicles

WRT dandwyer "problem" not sure what the definition of that is.  But to 
answer your other questions, yes retrofits to air locker is easy, you need a 
trans out of a 4kq.  The torsen can allocate 78f/22r >22r/78f based on a 
matrix of variables on the same cf front and rear.  A locker allows no "slip" 
between axles.  The rear axle on your 89 should have a locker with an 
electronic switch (between the seats) that the computer automatically unlocks 
at 25mph.  This electrono/pneumatic switch arrangement can be fitted to the 
older "lockers" (btdt) and you can also easily disable to the 15mph defeat.


Scott Justusson
'87 44tq lockers
'84 urq lockers
'83 urq lockers with electronic locker mod


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