The John Deere tractor has been one of the most popular riding tractor mowers produced. They lend themselves well to maintenance and repair, usually requiring only a few basic tools and steps. The drive belt receives its power from the engine and engages the transmission pulley. Idler pulleys put tension off the belt to keep the correct pressure on the belt while it rotates. Drive belts become worn, frayed or break after continuous use and age. The average home repair person, with the aid of his John Deere operator's manual, can replace a drive belt in a manner of minutes.
Place the tractor on a level, hard surface. Remove the key from the ignition. Use a socket to remove the negative battery cable. Set the brake. Turn the fuel selector switch to the "Off" position. Pull the lever to adjust the mower deck up to its highest level. Place two long wood blocks at each side end of the mower deck frame. Use the lever to lower the mower deck onto the wood blocks, taking tension off the linkage arms that hold the deck in place.
Pull the retaining clips using pliers from the top ends of the linkage arms. There should be four main linkage arms that suspend the deck. Pull the linkage arm eyelet off the frame posts. Remove the wood blocks from under the deck. Slide the deck out into the open. Look at the routing configuration of the old belt if it remains attached. If not, refer to your operator's manual for the belt routing diagram.
Remove any clumps of grass, twigs, stones and impacted mud from the inside the mower deck. Make sure levers and linkages look normal, with no breaks or bends. Use a whisk broom to thoroughly clean the inside of the mower deck. Use a damp rag to wipe the inside clean, including the pulleys tops and bottoms, and pulley grooves. Turn the driveshaft pulley by hand to access all sides of the pulleys.
Remove tension on the belt by using an end wrench to turn the centre nut of the idler pulley. The smaller idler pulley will sit between the main transmission pulley and the driveshaft pulley. Slip the belt off the idler pulley. If the drive belt has a metal guide near the driveshaft pulley, or the transmission pulley, remove it temporarily with a socket. Loop the belt over the driveshaft and the transmission pulley. Install the belt guides, if you have removed them, and tighten the bolts with a socket.
Thread the belt through the idler pulley locations, making sure the "V" part rests inside all the pulley grooves. Use a socket to turn the centre bolt on the idler pulley to relieve tension. Slip the belt onto the idler pulley and release tension on the idle pulley. Slide the mower deck back under the tractor. Place the wood blocks on each side under the frame.
Raise the linkage arms and connect the top arm loops over the frame posts. Manually snap the retainer clips over the arm ends. Use the lever to raise the mower deck to its highest position. Remove the wood blocks. Lower the mower deck to the floor. Reconnect the negative battery cable with a socket. Turn the fuel switch to the "On" position. Insert the ignition key and start the engine. Release the brake and test-ride the mower over a lawn surface, activating the mower blades.
Some tractor models, those with electric clutches, require the gear to the driveshaft be removed with a socket, to get the belt around the pulley.