An inter-axle differential (IAD) assembly including a unitary IAD case having one or more spaced-apart apertures extending therethrough, wherein each of the IAD case apertures defines a groove, and a spider having a plurality of radially, outwardly extending legs, wherein one or more of the legs include an opening at an outward end thereof, and wherein each IAD case apertures are aligned with each of the leg openings. The IAD assembly further includes a locking mechanism having one or more fastening elements, wherein the fastening elements are selectively inserted through the IAD case apertures and into the one or more leg openings and/or into the grooves of the IAD case apertures.