Real Four-Wheel Drive, Made Easy: The transmission in the four-wheel drive RX 300 features an integrated transfer case and a viscous center differential that provides a 50/50 front-to-rear power split. The system requires no activation by the driver. If slippage occurs at the front or the rear, the viscous center differential automatically and transparently directs power to the wheels with the most traction.
Auto-AWD is on the majority of the vehicles out there, like the JGC, Pathfinder LE, GM Blazer/Jimmy/etc., Acura MDX, etc. These are vehicles that normally supply torque to only one axle until slippage is detected and then transfer torque as needed. The JGCL (Quadradrive)takes this one step further by putting georotor couplings on each axle which allows side-to-side torque transfer independent of the front-to-back transfer.
Auto-AWD systems are reactive, permanent-4WD is proactive. The reactive systems will help you get "unstuck", the proactive systems will do this plus contribute to handling stability. Don't get me wrong, the Quadradrive system is the best off-road system in the world, but it doesn't out do the RX300 when it comes to highway stability.
The confusion on the different system names is a direct result of the "geniuses" in marketing
For a good explanation drew_ "4WD & AWD systems explained" Feb 5, 2001 8:24pm