That depends on the contact area. For example, The splines of axle shaft (which I assume is what your talking about) has a 100% contact area with the drive gears (no idea what the real name of the two small gears the axle slides into are called).
You're talking about spider gears in the differential? Or on heavy equipment, an axle shaft will have one splined end and one geared end. The spline end meets the spider gears and the (sun) geared end that meets three planetary gears.





