Here's a link to the parts diagram on the Sears Parts Direct web site. It should help you out with the routing. It sounds to me like there is either a problem with the belt routing or you have the wrong belt.
Hope this helps.
http://www.searspartsdirect.com/partsdirect/part-model/Craftsman-Parts/Riding-mower-tractor-Parts/Model-917254680/0247/1509200/00048814/00006?blt=06&prst=&shdMod=
Hope this helps.
http://www.searspartsdirect.com/partsdirect/part-model/Craftsman-Parts/Riding-mower-tractor-Parts/Model-917254680/0247/1509200/00048814/00006?blt=06&prst=&shdMod=