A drive shaft comprising: a first external crowned spline tooth including a first spline tooth side wall extending from a first base portion to a flat first tip portion of the first spline tooth, the first spline tooth further including a first midpoint region between the first base portion and the first tip portion wherein the flat first tip portion is located on an axial centerline and is orthogonal to a center axis of the drive shaft; a second external crowned spline tooth having a second spline tooth side wall extending from a second base portion to a flat second tip portion of the second spline tooth, the second spline tooth further including a second midpoint region between the second base portion and the second tip portion, wherein the flat second tip portion is located on the axial centerline and is orthogonal to the center axis of the drive shaft; and a groove defined by the first and second spline tooth side walls between the first and second spline teeth, and further defined by a root portion between the first and second base portions of the first and second spline teeth; wherein the first spline tooth side wall has a first crown drop at a base region thereof; wherein the first spline tooth side wall has a second crown drop at a midpoint region thereof; wherein the first spline tooth side wall has a third crown drop at the first tip portion thereof, the third crown drop being measured between two points along the first flat tip portion; wherein at least two of the first crown drop, the second crown drop, and the third crown drop are equal to each other wherein no portion of the first external crowned spline tooth is radially undercut and no portion of the second external crowed spline tooth is radially undercut; wherein the first external crowned spline tooth, the second external crowned spline tooth, and the root portion are each symmetrical about an axial centerline; and wherein the root portion located both at the centerline and angularly centered between the first external crowned spline tooth and the second external crowned spline tooth is concave, and any amount of crown drop associated with the root portion does not exceed any of the first crown drop, the second crown drop, and the third crown drop. a first external crowned spline tooth including a first spline tooth side wall extending from a first base portion to a flat first tip portion of the first spline tooth, the first spline tooth further including a first midpoint region between the first base portion and the first tip portion wherein the flat first tip portion is located on an axial centerline and is orthogonal to a center axis of the drive shaft; a second external crowned spline tooth having a second spline tooth side wall extending from a second base portion to a flat second tip portion of the second spline tooth, the second spline tooth further including a second midpoint region between the second base portion and the second tip portion, wherein the flat second tip portion is located on the axial centerline and is orthogonal to the center axis of the drive shaft; and a groove defined by the first and second spline tooth side walls between the first and second spline teeth, and further defined by a root portion between the first and second base portions of the first and second spline teeth; wherein the first spline tooth side wall has a first crown drop at a base region thereof; wherein the first spline tooth side wall has a second crown drop at a midpoint region thereof; wherein the first spline tooth side wall has a third crown drop at the first tip portion thereof, the third crown drop being measured between two points along the first flat tip portion; wherein at least two of the first crown drop, the second crown drop, and the third crown drop are equal to each other wherein no portion of the first external crowned spline tooth is radially undercut and no portion of the second external crowed spline tooth is radially undercut; wherein the first external crowned spline tooth, the second external crowned spline tooth, and the root portion are each symmetrical about an axial centerline; and wherein the root portion located both at the centerline and angularly centered between the first external crowned spline tooth and the second external crowned spline tooth is concave, and any amount of crown drop associated with the root portion does not exceed any of the first crown drop, the second crown drop, and the third crown drop.