...The B5 S4 which was essentially the first 6 speed box uses a unique Torsen.

I say unique becuase when the next 6 speed box came out (used for the 1.8t Longitudinal and the B6 S4) the Torsen changed.

Still the same design, but they moved one of the splines to the outside of the housing (not sure why, seems like a better, but more expensive design).

You can't put a B5 S4 6 speed Torsen into a B6 S4 6 speed transmission and vice/versa. Lame, but reality.

Now you've got this potential shift to a Type C Torsen. This will in all liklihood have no chance in hell of dropping in a B5 6 speed box. Best chance is that the entire B7 RS4 tranny will meet the B5 2.7t motor. Good news there is that Audi has kept that bell housing to motor connection pretty much the same since like a million years ago.

Type A (us):





Type C (bad ass):





Of course, I could be wrong, but from the sound of it, this is what Audi is doing, and I applaud them for that. Now they have an easy (relative) way to set static torque split between performance and general model variations.