my problem is my 2000 chevy blazer makes a loud roaring noise. when you drive in the city it's fine it's when your driving on the highway it makes this roaring noise and when you get off the exit and slow down it gets louder. but if i put it in 4x4 the noise goes away, it only does it on the highway. I've hade the axles replaced by the dealer and the noise is still there. it's been to two dealers and they dont know whats wrong. it's going to another dealer and maybe they can fix it but i doubt it. desperatly in need of help