One time I put mine on wrong and went under that hanging bar that holds up your mule drive. Yeah it worked but I smelled burnt rubber almost immediately. With the next belt consult your manual when you put it on so the belt threads under the pulleys but over that hanging piece of angle iron on the "QUICK DISCONNECT" assembly. That's a start, good luck.
dude, I'm running through PTO belts myself. Ebay is a very cheap source for kevlar belts - $33 + free shipping for mine - B108K. I'm going through one per season and it sucks bad... I'm starting to think I have an issue with a pulley.
I don't know if you have resolved this yet, but I had similar troubles with a PTO belt tearing up within 20 minutes or so myself. My machine is a GT2544 (2007 model).
There isn't much you can do wrong with these belts. The tension is set by spring.
After a lot of frustration, the dealer I bought it off of ground out some clearance on the front bracket. He felt the belt was flexing and the back of the belt was hitting the bracket. It seemed to prolong the belt breaking for almost a whole season, and then it would go again. I religiously blow the grass clippings off the deck each time I finish a section. I thought maybe the grass that packs under the pulleys was causing issues. Eventually the bearings in the double pulley went and I had a new one put on. This seams to have resolved my issues. That is until today.....they went again. I was able to get new bearings and install them.