John Deere Mower Belt keeps coming off: We have a fix

The John Deere brand is synonymous with exceptionally reliable and durable equipment of all shapes and sizes. A quick look at the manufacturer’s warranties will show you the level of confidence it has in every one of its vehicles and tools. Of course, the real world can occasionally present a set of circumstances that result in freak occurrences…or recurrences.

Mower belts slip and come off eventually even on well made machines like John Deere mowers. The problem could be several issues like extreme temperature, wear and tear, debris and mower deck positioning. Some fixes for belts coming off are simple and some require professional help.

Today we focus on a problem that is within the latter category. John Deere lawn tractors and mowers have been known to pick up mower belt issues over extended periods. The following article will explore causes and possible solutions for a belt that just won’t stay in place. Let’s get started!


Why does a John Deere mower belt keep coming off?

Interestingly enough, there are several reasons why your mower’s belt might come off…and keep coming off. 

Wear And Tear Can Even Cause John Deere Belts To Slip

The first and most common cause is good old wear and tear. The belt itself is prone to overstretching due to continuous use and exposure to different conditions. 

This may not be due to improper use or lack of care. Mower parts wear out with use over time and this goes for even well made parts.

Obstructions Can Be The Cause Of Mower Belts Slipping

Clumps of dirt, debris, rocks, and even accumulated grass clippings can get stuck between the belt and pulleys. This adds extra tension to the belt, which results in overstretching after a while. 

Here there is more than likely a failure to ensure the surface connections between the belts and pulleys are kept clean and free of debris. The good news is that it is an easier fix.

Extreme Weather And Temperature May Cause Mower Belts To Come Off

Another threat to belts is extreme temperature changes. This is a common problem in very cold climes. Repeatedly heating a near-frozen belt may also cause it to lose shape over time. Continuous use in such circumstances could also result in the formation of cracks before the belt finally snaps.

Check Pulleys Can Become Loose On John Deere Mowers

The pulleys are another thing to look out for if you’re having lawn mower belt issues. The belt is responsible for connecting a series of pulleys in the deck, which then allows the blades to engage and spin. 

The system works excellently provided everything (especially the pulley system) is working correctly. However, were any of the pulleys to become loose in their positions, the whole system would be compromised. This could be a hidden reason why your mower belt keeps flying off.

Other parts of the pulley-belt system can also get damaged or lost over time, resulting in loose pulleys, and a mower belt that just won’t stay in place. You or a trusty mechanic should inspect the mower for missing or damaged draft rods and rear hanger clip pins.

Mower Deck Positioning Could Cause Belts To Be Displaced

The positioning of the mower deck can also affect a belt’s ability to stay in place. Deere mowers, like most other lawn tractors, are fitted with mower decks with a slight tilt towards the front. As a matter of fact, for optimal balance, the front end of the mower deck is placed up to seven millimeters lower than the rear end.

If the deck’s balance is distorted for any reason, the belt may be more likely to slip off during operation.

If you ever wondered where John Deere lawn mower engines are made, then you will like my article here… Who Makes John Deere Lawn Mower Engines?

Why Do My Mower Belts Keep Breaking?

If your problem is resulting in mower belts breaking, you may have many of the same problems. If your belt is out of line with the pulleys or experiences excessive wear and tear, then it may simply break instead of slipping off.

You will not have to guess about whether you have a problem at this point and it would be advisable to investigate before simply buying a replacement belt. If one has broken due to a condition with your mower, it will more than likely happen again.

Go through the suggestions above and see if any of these could be the culprit. Correcting them before replacing the belt could save you a lot of time and money. Believe me, I have tried simply replacing parts before only to kick myself later when the same issue occurs.

A belt breaking is a definite sign that you may have one of the problems listed above. Yet, there are other signs or symptoms of issues with mower belts.

Loose mower belt symptoms

Let’s take a look at some of the common signs of a mower belt that needs attention. 

Loose positioning

If you know how the belt sits within the pulley system when the mower is new, you will have no problem identifying a loose belt. A quick glance can easily reveal how the belt is sat among the pulleys.

If the belt is hanging off the pulleys, even whilst fully engaged, then you know you have a loose belt. It will only be a matter of time before it begins flying off position entirely.

Reduced fuel efficiency

One of the more subtle signs of a loose mower belt is reduced fuel efficiency. If you notice that your mower is covering less ground on a specific quantity of fuel than normal, then there is a good chance that you have a loose mower belt on your hands.

A loose mower belt will not engage the pulleys and, ultimately, the blades as efficiently as it should, which means it will require more time (and fuel) to cut the same area as a mower with a taut belt.


Before a mower belt snaps completely, it can develop cracks and frays, just like a rubber band. This roughens the belt’s surface and continuous use will result in the cracks turning into burns because of the friction. These burns are known as “frays”.

This is a dead giveaway because belts in good condition have smooth and burn-free surfaces. If the belt is cracked, there is a good chance it is also loose.


As we discussed above, an overly stretched out mower belt may also develop cracks along its surface.

When the mower is in operation, these cracks will rub against the pulleys, causing friction and a discernable squeal.

How to fix a John Deere mower belt that keeps coming off

The very best way to fix a problematic mower belt is to get a new one. This is a key part of the mower, and it must be in tip-top shape for maximum efficiency. A cracked and frayed belt must be replaced before it snaps.

However, unless the belt is damaged beyond reasonable repair, there is a way to address a loose mower belt without purchasing a fresh one.

How to tighten the belt on a John Deere mower?

The first thing you need to do before handling the mower deck is to ensure the motor is OFF. Make sure to disconnect the sparkplug wires as well just to be safe.

  • Next, pull the lift lever to disengage the mower belt. The setting is usually labeled “transport mode”, depending on the model you have. 
  • Next, adjust the belt tensioner. This is usually a small cable sat in a metal bracket affixed to the mower deck. When the lift lever is set to a disengagement position, the tensioner cable loosens its pull on the mower belt.
  • To adjust the belt’s tension, you must shift the position of the metal bracket, which will in turn increase the tensioner cable’s pull on the mower belt. Unscrew the bolts joining the bracket to the deck. Move the bracket forward (away from you) to reduce tensioner pull or backward (towards you) to tighten pull.
  • Next, re-engage the lift lever, reattach the sparkplug, and test the mower.

Final Touches On John Deere Mower Belts Coming Off…

If any of these don’t seem to be the problem or it is beyond your abilities to fix, there are really two options. Bring your mower to a qualified mechanic or purchase a new belt and replace the old one.

Hopefully the information here can help you fix your problem and get your mower up and cutting again.


Mathew Booe

Mathew has worked in landscaping professionally for over 10 years. He is a grandpa and frequently interviews other experienced landscapers and lawn care experts who are also grandpas for these articles.

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