If you own your John Deere LX 279 lawn mower long enough, eventually you will need to replace the drive belt that connects the drive pulley to the mower deck. The drive belt's only function is to use power transferred from the motor's drive pulley to the blades mounted under the mower deck. Even with a built-in tension system called an idler pulley, the belt eventually stretches too much and requires replacement.
Things You'll Need
Drive your John Deere LX 279 onto stable flat ground, turn it off and set the parking brake.
Disengage the PTO lever to release tension on the drive belt and then lift the mower deck to its highest positioning with the lift lever.
Secure blocks under the edges of the LX 279 mower deck and then lower the mower deck onto the blocks. This holds the deck and prevents it from falling.
Remove the bolts that secure the mower deck to the brackets mounted under the lawn mower with your wrench. You will locate three mounting brackets, one on each side of the mower deck and one in the front.
Slide the deck forward slightly and pull the drive belt off the drive pulley mounted under the mower's engine.
Pull the deck out from under the mower and then remove the remainder of the belt form the LX 279 mower deck. If you need to, make a diagram of the belt routing before you take the belt off. This will help you when you put the belt back on.
Wipe the old grass and debris off the mower deck with a rag.
Place the new belt onto the mower deck and then slide the mower deck back under the mower.
Place the drive belt over the drive pulley and then line up the holes in the deck with the mounting brackets.
Secure the deck to the mower by reinstalling the bolts and then remove the blocks from under the deck.