The mower belt on a John Deere lawn tractor constantly is exposed to dirt and debris during the mowing season. This wear and tear makes the drive belt one of the most vulnerable components on the tractor. To prevent unscheduled seasonal down time, check the belt each year before putting the mower to work. Inspect the exposed rubber vee section of the belt for cracks. Also look for loose threads and signs of fraying on the back of the belt. If in doubt, replace the belt. Keep the old one as an emergency spare.
Drive the tractor onto a clean level surface, and engage the parking brake. Turn the engine off and remove the ignition key. Pull the mower belt drive engagement lever back into the "off" position and lower the mower deck all the way.
Work from the left side of the tractor and remove any loose debris from the belt area on top of the mower deck. Inspect the decal on top of the deck to familiarize yourself with the belt layout.
Insert a 13 mm socket wrench onto the idler pulley fitted with a tension spring. Apply clockwise pressure to move the pulley back. This process will loosen the belt. Reach toward the front and remove the belt from between the engine pulley and the pulley guidepost while maintaining tension on the idler pulley with the socket wrench. Note: This step only applies if your particular John Deere model is fitted with an electric clutch that applies constant belt tension. If not, moving the mower belt engagement lever to the "off" position will release the belt tension prior to removing the belt from the engine pulley.
Strip the belt from both idler pulleys. Use the correct size socket wrench to remove the two securing bolts from the mandrel guide cover plates if your tractor is fitted with cover plates. The mandrel pulleys drive the mower blade shafts. Lift the belt from between the mandrel pulleys and the pulley guideposts.
Use the 13 mm socket wrench to check and tighten all pulley securing bolts. Inspect the pulleys for warping, stone damage and dirt buildup. Clean the pulley working surfaces with a rag and an evaporating cleaning solvent. Dry thoroughly.
Install the new belt around both mandrel pulleys. Ensure that the belt is on the correct side of the mandrel pulley guideposts.
Loop the belt over both idler pulleys with the belt on the correct side of the pulley guideposts.
Release the tension on the first idler pulley with the 13 mm socket if the tractor is fitted with an electric clutch. Reach forward and slip the belt over the engine drive pulley.
Check the belt configuration against the decal on the top of the mower deck. Ensure that the belt clears each guide post. If the tractor has no electric clutch, engage the mower belt drive engagement lever before inspection.
Replace the mandrel guide cover plates with their securing bolts and the correct size socket wrench.