ok so ive been noticing a rather loud humming noise in my 99 3.4 alero and its bugging me....it started about a week ago and i cant figure out what it could be. it wont happen until i get above 40mph and it sounds like a grand prix exhaust , its not too bad but i want to get it solved b4 something goes wrong.. then once i go under 40 it will go away.. so idk its just a loud humming noise , and my exhaust is brand new from the cat back.
how much would that be and how can i be sure? but when i get on the highway and get to about 60 or higher i dont hear it anymore..its only about 40-55 mph