Posi-Traction is not the answer. Unless you are a stunt driver posi on snow is tricky. When you turn a corner the outside wheels travel further than the inside. If you lock them up, the rear wheels will push you right through the corner, or you have to risk losing control and stab the throttle for a power slide-OK on dry pavement, but not so on ice. I live in central Alberta Canada, and we get snow as well so I speak from experience. The answer is more weight, or maybe studded tires. You drive a light truck with lots of power, so traction comes from weight. Try building a frame to cover the floor with a plywood top and fill it with rocks or concrete you'll gain a couple hundred lbs which is probably closer to what you need. 50lbs worth of sand works in in the trunk of a Cavalier, but your Ranger actually has power.