OK, let's see if a schematic helps. This is not a BMW, it is a Ferguson. Same principle. It had a 37:63 torque split. That is due to the geometry of the planetary cluster used.

Ignore the limited slip, you don't have that feature.

See the planetary cluster on the right. The input shaft is connected to the carrier. The rear driveshaft is connected to the ring gear. The front driveshaft is connected through a chain to the sun gear.

The planet gears don't rotate on their shafts unless there is relative rotation front/rear, although they always spin with the carrier.

Jeff

Attached Images

 

__________________
2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue