I'm having a slight issue my rear wheel (stock Kilo TT wheel), specifically the hub/axle.



The driveside of the hub/axle is fine. The non-drive side, when I attempt to remove the nut, the piece with the black arrow above it turns in the same direction, so I have to use a 2nd wrench to hold it still while I unscrew the outside nut (red arrow).

When I completely remove the nuts, leaving just the piece with the black arrow above it on both sides of the hub, I'm not sure if I'm supposed to tighten them or not. When I tighten them, hold the axle, and attempt to spin the wheel, the wheel doesn't spin. Does the piece under the black arrow have a name? The driveside one is tight and the non-driveside one is loose, allowing the wheel to spin relatively normal. It seems I can unscrew the piece, but then when I do, the metallic gray piece begins shifting left and right inside the hub when I jiggle it.

I'm wondering if the hubs and bearings need servicing as well, as the rear-wheel doesn't appear to spin as freely as it could.