I can not stress enough the benefit of buying the JD technical manual for your mower.
People wince at the cost but it is not much more than the belt which you now may have destroyed.
I do not have one for your model but below is the proceedure for an LT 133 to LT 166
On decks with manual PTO engagement having the right side spindle brake working is vitally important as that is what causes the belt to slack to accumulate around the engine pulley
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