Cruise Control problems of the 2004 Cadillac CTS

Had my cruise control set at 70 mph for highway driving when I heard a psshhh sound and cruise control broke violently and smelled burnt rubber with smoke coming from back end of car. Pulled over immediately and car smoke from back end and smell only increased. Thought for sure I had a tire blowout. Walked around car and nothing wrong with tires. Had car towed to an auto repair place and am told that the rear differential went out. I have since investigated and found many, many forums about this issue. There are no recalls for this particular model but a certain recall for 2005 models. This situation could have been deadly and I feel both fortunate and upset with gm that such a problem has been so commonly noted but with no "real" resolve. The auto repair place has called around and this is a special part that is not available in my state and a new one costs an estimated $1,200. With so many issues with models 2004-2006 how come there is no recall for 2004 and only a lesser degree of a recall for 2005?.