The other day I had the unfortunate experience of backing off the edge of a driveway on a steep hill. I had the drivers side front wheel on the concrete driveway and the other three wheels on the grass. When I tried to drive back onto the driveway the front wheel on the concrete would just spin and the other wheels did nothing. I had to be pulled back onto the drive by a Ford pickup. "Embarassing" . Why did the all wheel drive not engage? I went ot the dealer and got what I think is a poor explanation.