The current parts number 19148847, which available from several GM online suppliers - none are cheap. That part number is for the current replacement axle which is 1.50 inches in diameter as opposed to the original 2005 version which was only 1.25 inch in diameter - so if you look at used units the part number will differ. Additionally, since a number of CTS-V owners have converted to aftermarket axles there should be some available. If you have the time you might check the classifieds of all known CTS-V forums. Finally, you could go aftermarket e.g. GForce.