The VC doesn't effect the torque split until wheel spin occurs. The torque split is done using planet gears.

The drive from engine comes to the planet gear carrier (green) which makes the entire assembly rotate. The sun gear (yellow) takes the drive to the rear prop shaft and the annulus (red) drives the chain for the front prop (quite sure it went that way...). The VC is connected to brake any speed differences between the annulus and sun. The ratio of teethcount on the sun/planet/annulus gears dictate the torque split ratio. The smaller the sun gear compared to the planet gears, the less torque goes to the rear.