Driveshaft problems of the 2006 Porsche Cayenne

In 2013 I had the rear differential replaced for 1600 now I am experiencing vibration at initial takeoff took it to the dealer was told it is the rear driveshaft that needs to replaced again and the cost is 2400. 00. Per the web there has been a lot of complaints for this same problem why hasn't there been a recall? what is the process to get a recall for this problem?.

Upon returning from a 200 mile trip cruising at 60-65 mph and exiting the off ramp at lower speeds (25-30mph) my vehicle began to shake violently and stop upon coming to a complete stop. Once I started to accelerate the vehicle again began to shake violently and loud knocking came from the under carriage. I took the vehicle to my mechanic and he said there is a failure in the center drive shaft support bearing and has seen this in ever Cayenne he has serviced. I also looked this up online and found many complaints and service tech's talking about this failure around 70k-90k miles for ever Porsche Cayenne and vw toureg. I hope there is some manufacturer financial support for this obvious defect which should have been recalled a long time ago.