Craftsman GT18 Throwing Mower Deck Belt

Guys,

I have a Craftsman GT18 (917253741). When I disengage the mower deck, it throws the belt. I bought a new belt, thinking the old one was just worn and stretched out, but it still does it. Any ideas?

Thanks

CONSIDERING THE AGE OF THE MOWER I DOUBT YOU HAVE OWNED IT ALL IT'S LIFE. MY EXPERIENCE IN THIS CONDITION IS THAT SOMEONE IN THE PAST HAS LEFT OFF BELT GUIDES OR GUARDS OFF. BEST BET WOULD BE TO FIND ONE LIKE YOURS AND TAKE A LOOK AT THE GUIDES. BLESSINGS JIMMY

I was actually thinking the same thing. So if anyone has a picture of this mower deck that would be awesome! Not sure exactly what size it is but it only has one pulley on top and 3 15 1/2 inch blades.

Thanks again
Wayne