How you go about measuring an axle depends on the axle type. Axles with yokes (front axle shafts) are measured from the center of the u-joint bore to the end of the splines. Semi-float and C-clip-equipped axle shafts are measured from the end of the shaft to the outer edge of the mounting flange. Full-float designs are measured from the spline ends to the front surface of the mounting flange. Check out the accompanying schematics for more on how to measure each axle type.