Basically, there's a Power Take Off (PTO) off the trans up front that sends power rearward via the drive shaft (prop shaft). Right in front of the rear diff, there's a computer controlled clutch. Normally, this clutch is open (i.e. does not transfer torque). End result, you've got a FWD car that's just toting around all the AWD hardware. When the AWD computer figures out that you need more power sent to the rear, it progressively applies the clutch, effectively locking the rear axle to the front.
The tricky bit is how the AWD computer figures out when you need more power to the rear. Really simple systems just wait for the front wheels to spin, but the Dodge system looks at stuff like throttle position, vehicle speed, steering angle, etc. so it can make your car AWD before you start spinning the front wheels. This makes it a proactive AWD system as opposed to a reactive AWD.
Functionally, Subaru's Automatics, and the VW/Audi Haldex systems seem to be similar. No idea exactly what the Dodge AWD ECU uses to figure out what to do and that's probably proprietary anyway.
" All-wheel drive. Very good. It whipped through a heavy snowfall with little wheelspin or hesitation. It had no traction control. That comes as part of the stability system available later this year. No guarantee that will make the AWD work any better.
The AWD system is a front-driver that starts shuttling power to the rear wheels in two different circumstances: when the road is slick and sensors believe the fronts are slipping or soon will be, and when you're driving vigorously and sensors say the car would be more stable with power at all wheels. "
The AWD works very well, we were on a very muddy road, travelling at a "unsafe speed" as my wife was yelling and gripping the shit handle above the passenger door. We went into a corner and the rear started to slide, then POOF, it straightened out and was fine.