I need some help to determine what is the problem with my 2001 BMW X5 4.4i, when I shift gear I always hear clicking noise, now when I put in "Reverse", the whole car shook and sometimes I back up ok and sometimes I have to do reverse a few times in order to backup. Does anyone have any idea what seems to be a problem? I heard some people said I have the bad axles, is it true? Please advise.