The forum won't let me post a link until I have three posts... You can search Youtube for "John Deere x300 mower belt breaking prematurely"
I found another way to fix it. May or may not work for you. First, make absolutely sure that the mower is leveled. This is important, because you're going to cut a chunk off the socket head screw (part M164280, shown as 26B on JD diagrams at XXXX://partscatalog.deere.com/jdrc/sidebyside/equipment/68603/referrer/navigation/pgId/2424937) --replace XXXX with the proper command.
That's the bolt that holds the mower up. Examine that bolt on the right hand side ("passenger" side) of the mower. You will likely find that the belt rubs against it and/or the nut that holds it in place. If so, you can cut the excess off. At the same time, make sure that the "lift link" (part M164279, shown as 27B on the previously referenced diagram) is placed so that the longer side faces up. (This will make sense when you disassemble the bracket.) With the longer part of the link facing up, it's actually possible to put the nut behind the bracket, which clears the belt. In order to tighten the nut, however, you have to prop up the right hand side of the mower deck to expose the nut. I did it with a piece of 2x4 on edge.
I found another way to fix it. May or may not work for you. First, make absolutely sure that the mower is leveled. This is important, because you're going to cut a chunk off the socket head screw (part M164280, shown as 26B on JD diagrams at XXXX://partscatalog.deere.com/jdrc/sidebyside/equipment/68603/referrer/navigation/pgId/2424937) --replace XXXX with the proper command.
That's the bolt that holds the mower up. Examine that bolt on the right hand side ("passenger" side) of the mower. You will likely find that the belt rubs against it and/or the nut that holds it in place. If so, you can cut the excess off. At the same time, make sure that the "lift link" (part M164279, shown as 27B on the previously referenced diagram) is placed so that the longer side faces up. (This will make sense when you disassemble the bracket.) With the longer part of the link facing up, it's actually possible to put the nut behind the bracket, which clears the belt. In order to tighten the nut, however, you have to prop up the right hand side of the mower deck to expose the nut. I did it with a piece of 2x4 on edge.