Ever since the CTS-V was introduced in 2004, owners have reported rear differential problems and failures. However, GM has paid little attention to us and not provided us with a fix for this problem. As Cadillac's flagship performer, the CTS-V is plagued with rear differential howling and whining. Not only that, the rear diffs have been reported to seize up and completely grenade. There is no doubt that GM is aware of this problem, as the 2006 CTS-V got a beefed up version of the previous differential, with a new part number. The following is a compilation of reported rear differential failures and problems found in the CTS-V. *Please note that it is not our intention to 'bash' GM or Cadillac. We are enthusiasts and fans of this car, and only want GM to fix our problem.* NHTSA (National Highway Traffic Safety Administration) Office of Defects Investigation - 2004 CTS/CTS-V Rear Differential Incidents NHTSA (National Highway Traffic Safety Administration) Office of Defects Investigation - 2005 CTS/CTS-V Rear Differential Incidents 15 pages of rear differential problems at CadillacForums.com Complaint of rear differential whine at CadillacForums.com Members discussing how many rear differentials they have gone through at CadillacForums.com 2004 CTS-V gets newer updated 2006 differential under warranty- WHINE IS GONE The result of a whining rear differential that was not fixed; broken axle New rear differential part number Owner on third rear differential due to whining Cadillac offering free extended warranty on rear differentials Discussion on how the new rear differential (2006 and up) eliminates the whining found on the 2004 and 2005 CTS-V More reported whining from CTS-V Rear diff whine gone after rear diff replacement And the list goes on... SIX pages and GROWING for posts regarding CTS-V rear differentials