The system never really locks as it does in a 4WD system. I had the opportunity to dig and drive my CX-9 and a 4WD Chevy Tahoe out of 18 inches of snow a couple weeks ago. The difference is very clear. The Tahoe was in 4WD lock and with just a little extra gas it blasted through the snow as if it wasn't even there. The CX-9 was a different experience entirely. You could feel the AWD system "figuring" things out and varying the power front/rear and probably applying the brakes to stop wheel spin. At the end of the day, the results were the same as the CX-9 got through no problem. You could just tell that the 4WD of the Tahoe (plus the added ground clearance) could have handled a whole lot more while the CX-9 was just about at its limit.