Steering Column problems of the 2008 Nissan Sentra

For a year or so my steering has begun to shake and make a clicking sound, especially while going down a hill and applying the brakes. At first I thought it was my brakes, and I took the car to my mechanic. However, after an inspection of the entire vehicle, my car received a clean bill of health. Even the brakes were in great condition. The mechanic did witness my complaint while road testing the vehicle and informed me that it seems to be a design flaw in my steering column. He offered to order parts and replace the damaged component, but my car is not even three years old! the clicking can also be heard when the car is in park and you just turn the wheel from side to side. The clicking was barely noticeable at first, but after about six months it became progressively worse. Now it is loud enough and my wheel shakes so badly that my passengers ask me what is wrong with my car. Something is just not right.