How to Replace a Transmission Belt in a John Deere L120

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The transmission belt on a John Deere L120 acts as an intermediate belt between the power take off, or PTO, clutch pulley, mower deck and transmission. Fortunately, the belt is attached to a spring-loaded tensioning system called an idler pulley. With the idler pulley, you can quickly release tension on the transmission belt and replace the belt within a few minutes. The only time you must replace the belt is when it starts to dry rot or you feel the transmission slipping when in gear.


Step 1

Place the John Deere's lift lever in the lowest position to drop the mower deck.

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Step 2

Locate the drive belt that connects between the PTO pulley under the engine and the idler pulley for the belt on the mower deck. The idler pulley has a bracket connected to it that allows you to pivot the pulley. This makes it easier to locate.

Step 3

Place a 15-mm close-ended wrench onto the nut on the idler pulley bracket and rotate the idler pulley away from the belt.

Step 4

Lift the belt off the PTO clutch pulley, idler pulley and transmission pulley at the same time.


Step 5

Install the new belt. Do not allow the idler pulley to move once you move it away from the original belt. You might need the help of a second person to remove the old belt and install the new belt while you hold the idler pulley in place.

Step 6

Move the idler pulley back against the belt slowly. The idler pulley is under tension and will spring back quickly if allowed.

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