9bolt rear end trouble

i have a 1987 iroc 5 speed 305tpi and it has a 9 bolt with disc brakes but I only get one tire fire is my rear end done or in need of help or not possi And i also get a viberation at about 50mph

it is not possi, and the vibration is most of the time normal, but at 50mph it is not that normal. It could be a drive shaft out of balance or the harmonic balener is bad.