If your tires are pointed out(left and right) then it can cause a vibration type feel. What is happening is the tires are fighting wich way to go. The general rule is for RWD and 4wd is to have a little bit of toe in, FWD toe out(the drive tire will want to create toe in going forward) and AWD generally will be closer to zero. Again that is just a general rule and manufacturers specifications should always be followed.I thought alignment prevented drift/pull/wear issues not vibration issues