6. Here you can see a portion of the new inner axleshafts. The top unit is the Yukon alloy shaft and the bottom is the stock shaft. The differences between the two are significant. Not only is the 4340 material far stronger than that used on the stock shaft, the Yukon alloy shaft is the same diameter from yoke-to-spline (the stock shaft necks down near the yoke); the yoke is machined to take stronger full-circle U-joint clips; and there's much more material in the yoke area overall. Most Dana 60 axles are 35-spline at the differential, so there's no increase in differential spline count.