I'm not an expert on this, but I think the axles are beefier, the front and rear differentials include (low pressure air?) lockers (and have lower gears), the transfer case is beefier (and has lower gears), there is a disconnect-able sway bar assembly up front, there is a switch panel on the interior with the locker activation switches. The drive shaft might have a longer yoke spline or universal joint over a non-Ruby (I'm not sure) to correct pinion angle when lifted. I think there are rock sliders and better skid plating also. The tires are available everywhere, as a lot of people upgrade in tire size and style, so they aren't really worth a whole lot. For example, I got brand new 32" take-offs from a Gladiator for $400 for 5.