Have to start in gear then have to shift on the fly with clutch all the way to the floor when I crank in Rev or 1 it's already rolling no noise but have to float the gears like in a big truck guy I got car from said needed a throw out bearing but I would think it would be making noise I'm new to the Mustangs I've always had Camaros but none of them has ever been like that it acts like the clutch has air in it and needs bread sure would appreciate the help stay strong pony boy 
