Transmission questions

[Dave]

the op is correct. a torsen is "locked" in normal conditions.

however, in "locked" state, the output shafts can move a little relative to
each other, it is this movement that forces the friction gears to resist and
the torque to go to the other side of the diff.  in this state torque moves
from side to side of the diff as traction conditions dictate (just as with a
standard locking diff).

the torsen "unlocks" when traction conditions force it to operate beyond the
"bias ratio" (usually 3:1).  At this point the friction gears "give up" and
allow the shafts to rotate relatively, but still hold the torque split at
the bias ratio.

the major limitation occurs when one side of the diff has limited traction
but the other has good traction.  "biasing" limited torque by 3 still gives
limited torque to the wheel that can take a lot more.  hence audi's edl
which is designed to use the abs system to brake a spinning wheel and force
torque back into the system. ultimately the "sport diff" in the rear
provides a much better solution to this issue.

dave
'03 rs6
'04 allroad tdi


> From: Mark R <speedracer.mark at gmail.com>
> 
> This can SO get out of hand.....
> 
> (I think) Torsens are never locked.  Locked means 50/50 split, no matter
> what.  Both axles (or wheels) turn always in sync.  With A Torsen this only
> occurs when driving straight and level, and it's still not "locked,"  Does
> that make sense?
> 
> On Sat, Apr 25, 2009 at 2:02 PM, Tony Hoffman <auditony at gmail.com> wrote:
> 
>> A TORSEN (TORque SENsing) differential only allows a certain amount of
>> slippage, as the gears essentially slide from one side to the other.
>> then, after that, it's essentially locked. At least, this is my
>> understanding from the literature and pictures I have in my possesion.
>> And, it would explain the driveline bind when on the gas at low
>> speeds.
>>