Locate the deck height adjustment lever on the right rear fender and move the lever to the bottom notch. This lowers the deck away from the tractor and gives you more room to work.
Locate all of the belt guards mounted on the mower deck and remove the screws that hold them in place with a Phillip's screwdriver.
Locate the belt keeper that mounts over the drive pulley on the bottom of the Cub Cadet's motor. Remove the bolts that hold the keeper in place with a socket and then place the keeper off to the side.
Locate the idler pulley bracket. It is the only pulley mounted to a spring-loaded bracket. Place the square end of a 3/8-inch ratchet driver into the square hole on the bracket and then rotate the bracket inward with the ratchet to loosen the belt.
Pull the belt off the pulley system on the mower deck and then pull the belt off the drive pulley under the motor.
Place the drive belt onto the drive pulley under the motor and then onto each pulley on the mower deck other than the idler pulley.
Push the idler pulley inward and place the belt around the pulley. Let go of the idler pulley to restore tension to the belt. Remove the ratchet from the idler pulley bracket.
Secure the belt keeper and the belt guards to the mower.