All riding mower belts wear over time. A worn belt usually begins to squeal when it is worn or stretched as a result of slipping on the pulleys. In addition, small cracks around the circumference of the belt is a sign of age or dry rot. Either condition is an indication you need to replace the belt on your Toro mower. Toro recommends you only use factory approved belts on your mower.
Lower the mower deck to the bottom notch on the deck height adjustment. From this position, the mower belt is more accessible.
Remove the pulley guards from around the main blade pulleys by taking out the self-tapping screws. A large Philips screwdriver or ratchet and socket will access the screws.
Make a mental note, or draw a simple diagram, of the belt's routing in the pulleys. If a diagram is not available in the operator's manual or from some other source, this is a time-saving step.
Take the tension off the belt by placing the 3/8-inch drive ratchet into the square notch on the idler sprocket. After inserting the ratchet, move it in a clockwise direction to relieve tension. The idler holds tension on the belt--even when the mower is not engaged.
Slip the old belt off the idler pulley and the PTO clutch (drive pulley). Once belt is free of the two pulleys, maneuver it free of remaining pulleys and set it aside.
Start the new belt on the pulleys in the reverse order. The idler and PTO clutch pulley are the last two parts to install the belt. Refer to the diagram you drew earlier as a reference.
Insert the ratchet into the idler pulley notch when ready for final belt installation. Rotate the idler clockwise and wrap the belt around the PTO clutch and idler pulleys before releasing tension.
Reinstall the belt guards and insert the self-tapping screws. Use the screwdriver or ratchet and socket to secure the screws in place. Start the mower and slowly engage the blades to ensure the belt tracks on the pulleys properly.