Honestly, I don't know much about simplicity decks. Is this something that has just developed or has it always been a problem? How long have you had the tractor? Can it be the belt is stretched or the pulley or cover is misaligned? For a 2002 I wouldn't think anything could be totally worn out yet but you may have a better idea of the service its seen.
Please don't be discouraged by the lack of responses. Most people here try their best to give honest helpful information rather than just pretending to be able to solve all problems.
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