How To Put a Belt on a John Deere Lawn Mower


Your John Deere mower uses a belt drive to transfer engine power to the wheels and the blades. If the belt is old, cracked, broken, or too loose, your mower will lose power. In some cases, if there’s enough damage, the blades might not turn. You might also not even be able to drive your mower forward. So, if you inspect the mower and see damage to the belt – replacing it is likely a cheap and relatively easy fix. However, the process of changing the belt on a John Deere lawn mower will vary slightly depending on which model you have. 

However, if you have a 100 series John Deere, replacing the belt is normally the same across all mowers. For example, the D140 deck must be removed to replace the belt. That holds true with almost any 48-inch John Deere mower deck

John Deere belt replacement normally means you have to take off the mower deck. From there, it’s a simple matter to remove the belt from the pulleys. In most cases, you can take the belt off, put a new one on, and adjust mower deck belt tension in as little as a few hours from start to finish. If you know what you’re doing, you’re probably looking at less than an hour. 

How to Change Drive Belt on John Deere Mower 

If you want to know how to change the drive belt on John Deere riding mower tractors, you can normally get started with just a few simple tools. These include: 

  • Safety gloves
  • Pliers
  • 15mm socket for the pulleys OR adjustable wrench  
  • 10mm ratchet OR adjustable wrench 
  • Belt – Belts are sold based on deck size. However, you can also reference the GXl number on your John Deere lawn mower to look up the specific belt for your deck. 
  • Flat screwdrivers
  • Lift, wood blocks, or lawnmower jack (optional)

Removing Belt 

In most cases, you’ll have to start removing the belt by removing the mower deck. That’s true with most popular models, including 100 series and 500 series John Deere mowers. 

Remove the Deck 

Park your John Deere tractor on a flat, hard surface. Follow safety protocol and turn the engine off, take the key out, and unplug the red cable from the battery. 

  • Lower the deck to its lowest setting.
  • Use the pliers to pull the pins connecting the deck to the stabilizer bar at the front of the deck. It’s best practice to remove the bar if you want to move the tractor. 
  • Remove the pins connecting the stabilizer arms to the deck. There should be at least two on each side. However, the larger your deck, the more pins there will be. 
  • Pull the pins from the hanging arm. Lift the mower deck and slip it out.
  • Remove the pin connecting the PTO cable and then pull the cable out. Undo the spring attaching the spring.
  • Lift your mower deck using the PTO lever.
  • Use the 10mm socket or adjustable wrench to take the belt cover off.
  • Slip the belt over the pulley so that you can slide the mower deck out.
  • Slide the mower deck out from under the mower.

Remove the Belt 

Use the adjustable wrench or a 15MM socket to loosen the bolts on top of the pulleys. You may want to block the pulleys to prevent them from turning while you’re loosening the pulley. The goal is to get the pulley high enough up to get the belt in without having to push the belt around the guide. 

  • Check the belt against the other belt. 
  • Rotate the idler arm counterclockwise to release tension off the belt.
  • Double check the belt threading guide in the manual.
  • Thread the belt around the pulleys using the guidance in the manual. 
  • Always put the flat size of the belt against the flat pulleys and the V part of the belt against the V-pulleys.
  • Double check the threading.
  • Tighten up the guides.
  • Re-tighten the pulleys.

Replace the Deck 

  • Slide the deck back under the mower.
  • Adjust the deck adjustment lever all the way down.
  • Lift the deck and re-attach the front stabilizer bar on the mower.
  • Re-attach the stabilizer arms on either side of the deck.
  • Lift the mower deck to re-attach the hanging brackets on each side.
  • Re-thread the blade engagement cable – being sure to thread under the break bar – and hook the spring back. on the deck. Re-attach the pin.
  • Loop the belt on the front pulley, inside of the bracket.
  • It’s usually a good idea to grease the edges of the new belt. However, some belts don’t need this. Check the back of the package for best practices. 
  • Engage the mower deck and make sure everything lines up and has good tension.
  • Put the belt covers back on.

Some John Deere tractors will require that you rotate the idler sheave in order to put the belt on. Others do not. Check with your model to see how it works. However, if you put the belt on with the deck disengaged, it should be relatively easy to figure it out. 

In addition, it’s always important to check the manual to ascertain that you have the belt configuration right. 

When to Replace JD Lawn Mower Belt 

John Deere tractors require regular maintenance to stay in good condition. Replacing the belt for riding mower decks is part of that maintenance. However, with good care, you shouldn’t have to replace the belt more than every 2-4 years. However, there are always reasons you might have to replace the belt more often. For example, if your John Deere mower belt came off during normal use – it might be a sign to either replace the belt or adjust mower deck belt tension. It might also be a sign the belt guides are not tight against the belt. 

If you’re having issues with the blades engaging, blade power, or the engine skipping, it might be a belt issue. In this case, you should always stop and inspect the belt. 

To start, follow the instructions to remove the deck from the mower as listed above. 

Examine the belt to look for damage. For example, cracks, chips, burns, etc. If the belt is loose, you also want to look at why. 

Brake Pads

If the brake pads are worn down, the metal brakes can eat into the belt. This might cause significant damage and will cause your belt to wear out more quickly. Normally, you can recognize this issue because you hear a loud metal-on-metal screeching sound when disengaging the blades. If you do, the answer is almost always to install new brake pads. 

Chips or Cracks

Deck belts can chip or crack when you hit objects, when they’re exposed to wet and then dry conditions, and when debris clogs the tracks. Here, you want to regularly inspect the pulley system to ensure there is no grass, debris, or other items in the pulley. Even clogged mud can cause your drive belt to break prematurely. 

Unfortunately, there’s little you can do about this. Chips and cracks usually happen when you’re mowing and objects or debris hit the belt. However, you can ensure that belt guards are properly installed to ensure you’re protecting the belt as much as possible. 

Belt Coming Off 

If the drive melt is coming off your mower deck, it’s likely a tension issue. Here, you can check several parts of the mechanism.

  • Check the tension adjustment and slide it to the tightest position 
  • Check that the belt guards are in place. If they aren’t up against the belt, you may want to tighten them into place. If they’ve bent out of place, bend them back. Here, the belt guards always have guides in the deck to show where they should be. If the metal flange at the end of the guard is not in the provided hole, the guard is not in the right place. 
  • Make sure the pulley sheaves are firmly tightened down. 
  • Check the belt tension and ensure that the belt isn’t frayed and stretched out of shape 

Most of these issues can be resolved by simply tightening some bolts, putting the belt guard back in place, or putting guides back in place. If that doesn’t resolve the issue, you may have to replace the belt to resolve the issue. 

Belt Breaking 

If your belt is breaking, it’s normally a sign that the tension is wrong, something is trapped in one of the pulleys, or something is catching. For example, your mower deck belt will break if one of the pulleys doesn’t turn. It might also break if rope, a stick, or other debris is blocking the path. Similarly, if one of the pulleys is bent or deformed, the belt might catch and break when you engage the blades. 

In some cases, belt breakage might also have something to do with tension on the engagement cable, if the brakes aren’t working well enough and the cable continues to move against the brakes for too long, or if the cable is simply old, frayed, and worn down. It’s important to check so you don’t lose a belt to the same problem twice. However, your mower belt can break simply because it is old. 

Burning or Glazing 

If your belt is smoking, burning, or glazing, it means the tension is wrong. In some cases, that means the tension is too tight and you’ll have to adjust the tension cable. In other cases, it means the belt is not threaded properly. Always double check the threading pattern with your owner’s manual to be sure you’ve put the belt on correctly. 

Cracks and Fraying

Cracked and fraying belts might simply be a sign of an old belt. On the other hand, they might indicate something is blocking the belt. They might also indicate that the belt is running too hot. These issues are normally caused by issues like tension being too tight, something being stuck in the mechanism, or built-up debris. 

Maintenance Tips

Replacing a John Deere transmission drive belt will normally cost anywhere from $25-$50 depending on the size and brand. In most cases, any properly sized belt will do. However, a good quality belt will last up to 4 years, if properly maintained.  If not maintained, your belt could last as little as a few months. So, spending a little time on maintenance can prevent extra costs and hassle. Here, good maintenance usually means regularly cleaning your mower and checking that everything is as it should be. 

  • Clean the deck after every mower use
  • Follow manufacturer care recommendations
  • Stop the deck and check the pulleys and mechanism if you hear screeching, squealing, or grinding 
  • Don’t wait too long to mow your grass. If you do, double check that nothing is jamming in the pulleys after mowing
  • Inspect the belt each time you change the mower oil 

Frequently Asked Questions

Riding mowers are relatively easy to repair. In most cases, you can easily replace a mower belt by yourself. However, if you still have questions, this FAQ should help. 

What size belt do I need for a 48-inch deck? 

It’s important to buy the right size belt when looking for a replacement. In most cases, the easiest way to do this is to check the John Deere’s GXL number for reference. This ensures you can find the right OEM part from John Deere. If you call your dealer with the GLX number, they’ll always be able to tell you the belt part number you need. Often, you can also find this part number in your owner’s manual. 

This is important because there is no standard size for a 48-inch deck belt. For example, some John Deere mowers use 92 inches, some use 85 inches, and some use 152”. The differentiator is in how many pulleys there are and in how the threading works. Always check your part number. If you don’t have the GXL number handy, you can try measuring the old belt. However, you should round down to the nearest 2”. This is especially important if the belt is old and may have stretched. 

Are all riding lawn mower belts the same? 

No. Belts vary in thickness, material, and length. Here, the standard thickness is ½”. In fact, it’s unusual to find a John Deere tractor with a different belt thickness. However, length can vary significantly. You should always double check the part number before buying a replacement belt. It’s also a best practice to check your new belt against the old one. Checking to ensure they are the same material, length, and thickness prevents causing problems in the mechanism. 

Fortunately, most John Deere tractors have a GLX number somewhere under the engine cover. This is normally on a visible plaque that you can easily refer to without 

What is the difference between a deck belt and a deck drive belt?

Many riding lawn mowers have two belts running the blades. Here, the deck drive belt is the long belt on the deck. It’s normally attached to a single pulley on the tractor itself. However, the rest is on the deck. Then, the tractor has a shorter belt that attaches the deck drive pulley to the engine. The second belt normally connects to either a third belt or directly to the drive shaft. However, the belt on the deck itself is more likely to be damaged, more likely to experience wear and tear, and normally has to be replaced every 2-4 years. The belt on the tractor itself is much less likely to require replacement and you might only have to replace it once over the full lifetime of the mower. However, that does depend on the mower, how you use it, and how you maintain and clean it. 

Conclusion 

The belt on John Deere mower deck pulleys keeps your mower working. It transfers rotary motion from the engine or clutch to the blades – so they engage and disengage when you need them to. If the belt is in poor condition, efficiency goes down. If the belt is broken, your blades won’t engage. In most cases, you can very easily replace the belt, sometimes in as little as a few minutes. If you calculate the time to buy a new belt, possibly call the dealership to ensure you have the right parts, and to acquire tools, you’re probably looking at a few hours of effort at most. 

If you do decide to change the belt on your John Deere mower, make sure you follow safety precautions outlined in your manual. You also want to ensure that you double check the belt threading before removing the old belt. The proper threading pattern should be in your owner’s manual. Otherwise, there’s very little that’s difficult about replacing the belt and you should be able to get your mower back in top condition in no time. 

If you need more help with your John Deere tractor, check our other guides for additional maintenance and replacement help.

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