i did mean clutch pack but from what i have seen from it working the torsen is not a LSD.
It will not force both wheels to drive but will favor the wheel with less traction
if it is supposed to make sure both wheels drive like a clutch pack LSD then i am not sure what was wrong with the one i saw...
either way the 3.91 i found was a nice compromise between the two so that you can keep the revs down for cruz'n but at the same time still have some nice acceleration. Also might be a good idea to replace the clutch pack in the 3.91 if it's getting on in the miles
NINJA Edit: I must have seen one that was messed up or something figured i should stop being stupid and look it up
http://en.wikipedia.org/wiki/Torsen
extra ninja edit this might be why i thought it was not as i was able to see one wheel getting most or almost all of the power as opposed to a clutch type diffy
How they work
The Torsen differential works by supporting a torque imbalance, the maximum ratio of torque imbalance being defined by the Torque Bias Ratio (TBR). When a Torsen has a 3:1 TBR, that means that one side of the differential can handle up to 75% while the other side would have to only handle 25% of applied torque. During acceleration under asymmetric traction conditions, so long as the higher traction side can handle the higher percentage of applied torque, no relative wheelspin will occur. When the traction difference exceeds the TBR, the slower output side of the differential receives the tractive torque of the faster wheel multiplied by the TBR; any extra torque remaining from applied torque contributes to the angular acceleration of the faster output side of the differential.
NOTE: The TBR should not be confused with the uneven torque-split feature in the planetary-type Torsen III. The planetary gearset allows a Torsen III center differential to distribute torque unevenly between front and rear axles during normal (full traction) operation without inducing wind-up in the drivetrain. This feature is independent of the Torque Bias Ratio.