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Toyota does. I know Dodge offered them on the powerwagon not sure if they still do. They are electronic. If you want lockers and money is not an option go arb. If you want to save a few bucks just pit a lockrite or a Detroit in the rear.
The reason there are so many Ruger upgrades is because they're necessary.
Because most people are four-wheel-drive retarded as it is!
Can you imagine all these pea brains trying to drive in the snow with all four truly locked in?