MY sons 1999 s 10 blazer has a weird rattle to it. It is more on the passenger side of the blazer. When you first start it up it is quiet but after a few seconds it starts to rattle. Sound like a rock bouncing around the bottom of a can or something. I have gotten underneath and tried to listen, but can't pin point it directly. I am wondering, if it is the flywheel that is cracked will the sound always be there or come and go at times like it seems this does.