The Model X will have AWD not 4WD.
4WD vs AWD: What's The Diff?
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I think the Model X will be able to claim all of the above. AWD and 4WD. With two motors it could replicate a true 4WD system, or a highly advanced AWD system, or ever a FWD or RWD system. That is why the potential of a dual-motor electric drive gives you.