A gear head friend of mine made himself a "real four wheel drive" by putting lockers on both sets of axles. There was no stopping the thing in a straight line he said, but the locker on the front came out real quickly when he tried driving that thing on ice. He described it as having a mind of it's own kind of like a pea on a platter.
When you turn, the outside wheel has to go farther than the inside. That means something has to slip. On ice, both of them can slip as they're pushed by the rears. It feels like they're going off 90 degrees from each other. I have a Polaris RZR. Admittedly it's not the road vehicle we're talking about here but the 4x4 principles are the same. On slick roads when the front is locked up, sometimes it will keep going straight when you turn because the locked rears have more traction and keep pushing it forward. The light weight fronts sometimes don't have enough traction to horse it sideways to overcome the heavier rears.
