HurricaneStang

About 2 weeks back me and my buddy put on the GT Take Off axel back and it seemed to be running fine. But the last couple days at idle or low rpms i noticed i've been hearing some sort of noise coming from the exhaust. It kinda sounds like its hitting on somethin. So i went back to my buddys house and we retightened all the bolts on the exhaust, which were tight already, so i didnt get what it was. I looked at bumper clearance and it wasnt touching it, i have about an 1/8" clearance to bumper. If anyone knows what this could be i'd be very greatful.