On dry surfce, the torque distribution ratio is 6:4. This ratio varies depending on the traction conditions.
Theoretically, it can send 100% of the torque to the rear wheels.

"If the front wheels slip, a viscous coupling directs up to 100 percent of the torque to the rear axle, and vice versa."

www.cars.com/carsapp/nati...going.tmpl

"A viscous coupling linked to the centre diff' can send all of the torque fore or aft in case of a loss of traction at one end."

4wd.sofcom.com/Hyundai/Sa...ta-Fe.html

"Santa Fe features full-time all-wheel-drive, its unique 60/40 front/rear drive split on normal paved roads matching the car's approximate kerb weight distribution. This ratio can vary either way according to load and/or changes in wheel grip conditions via a viscous-coupling of its front and rear drives..."

"On wet made roads or when encountering an unexpected slippery patch, Santa Fe's all-the-time all-wheel-drive offers the security of superior traction always being there without delay. This differs from the front-drive-only normal-road setup of CR-V or Tribute/Escape respectively, which, when slicker surfaces present, are tasked to divert some drive to their rear wheels. Significantly, this occurs only after their front wheels have already lost some or all grip and the time taken for their drive systems to divert the drive means valuable time may be lost in the transition."

www.autoweb.com.au/start_...ticle.html