Last Friday i noticed a huge vibration in my mower...first I thought was it was the blades, but it wasn't. Second thing I thought was maybe I forgot to grease up the deck, nope I just did it. Third thing was the belt. Yup, the main belt for the delt was torn all apart, but what could have done this. My cast iron pulley at the top actually broke off about 1/2 of its top piece. I have never seen anything like it before at all. How the heck could the pulley just break at the top?