I am slightly lost on exactly what you're looking for..? Most AWD cars are capable of running in a 2WD format with one of the driveshafts removed (some even 0WD as they use two driveshafts to drive two differentials).
Now I think I see what you're getting at. I believe the transmission sends a gearing ratio to an internal differential of sorts, which then drives the two front wheels via the front axles. The angle gear then drives (though the same internal differential, or another internal diff?) the prop shaft, which then goes to the rear diff/Haldex unit that we all know and love, which then drives the rear two axles.
You know most of this (if not all of this) already, but is that what you were referring to? When the Haldex unit is engaged, it "robs" power from the front wheels (I'd imagine equally from both front axles), and that power is of course put to the rear axles... so as long as the prop shaft and Haldex unit are hooked up, there is some power being robbed from the front two axles.