also your front rotors can be warped.. i heard that's pretty common... i think your front wheels are supposed to be torqued on at 75 ft lbs... if not they can warp..
humming i would think would have something to do with a wheel bearing or rear diff. i know they have rear axle seal problems so your gear oil can get low...take off you back wheels and if you have drum brakes pull the drum off and see if there is oil in there
ok i recently started getting a vibration around 35-40mph stops after that and around 65 it felt like i was driving on the rumble strip on the highway.. so the next day i figured it could be a something with the drive shaft so i greased all the zerks... now i have a mild squeak only when i'm on...