My Infiniti M37 knocks when I slow down, go over a bump, or turn my wheel. I was told my control arm needs to be replaced by an outside mechanic (not Infiniti) and we just had my car in for an oil change with Infiniti and they told us we need our steering rack need to be replaced. I didn't tell them what the other mechanic recommended. I wanted to see if they would come up with the same diagnosis. Now I don't know which one to believe. I was told over and over when I took my car to the Infiniti dealer that "This is our best mechanic and they really know what they are doing" This was after bringing my car in three times to figure out why may car was making a grinding sound after my brakes were replaced. It ended up being my rotors. They had already turned them and shouldn't have turned them again when they replaced my brakes. Anyway, they fixed the problem, but I would think Infiniti mechanics should really know these cars, and it shouldn't take three visits to figure out a problem