Your front end is probably out of alignment. Have it checked at a mechanic.
check your tires for broken belts or if see if some of your lead weights are missing.if belts in tires or if they are out of ballance it will cause vibration at 30mph or higher
I saw this on that Myth show. The body travels the same speed of the car which would be 45mph.
Someone did not reinstll the rattle clips. They are spring clips that snap into place and put tension on the pads. You will need to purchase some from Chevrolet parts and then have them print out a computer picture of how they snap in.
45mph
45mph
hi
45mph
45mph
45mph
45mph
45mph
35 to 45mph