Yesterday I was out to some friends property in the foothills. I attempted to climb a rather steep rutted driveway in reverse, only because of the lack of room to turn around. I made it almost to the top when the bed started bouncing, both tires were spinning and then the rear started to slide off the road. I tried this twice with relatively low speed in reverse, each time I had two tires spinning. I ended up turning around and driving up it forward in two wheel drive. The same thing happened it looks and feels like there is something other than an open diff in the rear of my truck. I stopped on the hill going up and rpm'd up a little and dropped the clutch again I had traction coming from both tires, pretty evenly. Although you could tell which tire started to spin first and which tire had the most traction. Do open diff's do this? Or is there a power lock in there? I posted a picture of my open rear diff a couple years ago and everyone said it was open. I just figured if it was open diff I would have only had one drive tire and been able to keep the truck straighter climbing the hill due to only one tire spinning. Maybe I should repost my picture?