Behold The Hyundai Uni Wheel. Transportation May Never Be The Same

Setting aside all of the already observed questions in the comments already about mechanical viability, i.e. how this assemblage is supposed to steer. The elephant in the room is whether or not this is equivalently economical to produce compared to an axle with a CV joint in it, and/or if it will acceptably reliable for roadgoing vehicle use, what with having a shitload more moving parts in there.

The animation shows the geartrain assembly in an open faced housing, which if that's how it's ultimately designed is going to mean that there is now no way to keep the gears in a bath of oil or transmission fluid like is presently done in traditional transmissions and differentials. And yes, even in CV joints which are packed with grease inside their rubber sealing boots. I'll let you in on a big automotive industry secret: There's a reason current transmissions and other geartrain devices are kept suspended in oil all the time. A big one. One that has to do with your transmission not glowing red hot by the time you make it to your destination, or converting itself into glitter within the first mile.

Even setting aside lubrication concerns -- Maybe the thing is chock-a-block full of sealed ballraces or something, for all I know -- the big open slot they depict for the axle to move up and down in is just begging for a stone, a stick, a stray bolt, or any other show-stopping piece of debris from getting in there and causing you to have a very expensive day. Ditto with the gap around the edge of the sun gear, which is going to need a bitchin' huge mechanical seal on it at the minimum. If the solution is perhaps to put some kind of rubber boot over the opening that moves with the axle, it's going to have to be ridiculously flexible and remain so even throughout all kinds of temperatures and operating environments. Cars, you know, being devices quite infamous for being operated outdoors in the weather and all.

I mean, I can't imagine Hyundai's engineers haven't thought of this. But I wonder if this is one of those works-in-the-lab-and-test-track things, and they're expecting someone else to figure out the viability challenges.