The Belt Keeps Coming Off Your Gravely Lawn Mower (Solved!)

When your mower belt comes off the pulleys of your Gravely lawn mower, it can be time consuming and a little annoying to have to stop mowing and reinstall the deck belt. It becomes increasingly frustrating when the belt continues to keep coming off your Gravely mower.

A mower belt can come off your Gravely mower when the belt is loose, worn or shredded; the belt keepers are damaged; the bearings are bad in the pulleys or spindle housings; the tensioner bracket or spring is worn; or debris is interfering with the deck components.

Read more about items that can cause your mower belt to not stay in place and function correctly. Follow your Gravely owner’s manual’s safety precautions while working on your lawn mower. This includes removing the spark plug wires and ignition key.

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Follow all safety instructions provided in your equipment operator’s manual before diagnosing, repairing, or operating. Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.

9 Reasons Your Belt Keeps Coming Off a Gravely Mower

Loose or Worn Mower Belt

A belt that is wearing or has become loose can come off your mower deck. A belt wears over time and must be replaced with a new deck belt.

Signs of a wearing belt are stretching, cracking or a shiny glazed appearance. A belt that sits deep in the grooves of your Gravely’s pulleys is another sign of wearing.

Mower Belt Keeper Damage

Your Gravely deck uses belt keepers to assist with keeping the belt in place. The belt keeper is a rod that sits between 1/8” and 1/4” away from the pulley and is used as a method of prevention to keep your belt from coming off the pulley.

The belt moves around your pulleys and doesn’t actually touch your keepers.

When you get slack in the belt, the belt can hit a belt keeper and bend it out of place allowing the belt to slip and come off your pulley. Fix your belt keeper by bending it back into place using a hammer or vice grip. If you can’t adjust it correctly, replace your belt keeper.

Shredded Mower Belt

If you notice shredding and torn edges on your mower deck belt, you must find the cause. Most likely, a bracket or belt keeper is out of place and your belt is rubbing against it causing the belt to shred. Another reason your belt can shred is when it is incorrectly routed around your pulleys.

First, make sure your belt is correctly installed. Refer to your operator’s manual or a parts diagram for the correct position of your belt around the pulleys. Second, find the item your belt is catching on when your deck is engaged.

Look for a shiny flat spot on a belt keeper or bracket. This is an indication you have an area rubbing against a piece of metal. Once you identify the part that is causing your shredded belt problem, adjust the part so it no longer rubs.

If the cause happens to be a bracket with a bushing, you may be able to replace the bushing. Sometimes you must replace the bracket assembly when the manufacturer only sells the part in this way.

Bad Bearings in the Pulleys

A pulley may no longer sit flat and parallel to the mower deck when the bearing is bad. A pulley with a bad bearing can cause one side of your pulley to sit higher off the deck than the other.

When this happens, your Gravely belt is more likely to come off the pulleys.

Check each of your pulleys to make sure they rotate smoothly and without restriction. Do this by slowly turning each pulley by hand. You will need to replace your pulley when you feel a restriction or hear a noise coming from your bearing.

Bad Bearing in the Spindle Housings

Much like a bad bearing in a pulley can cause your pulley to not sit flat, a bad bearing in your spindle housing can allow vertical movement in a blade that can cause the deck to vibrate.

This vibration can cause your belt to come off your Gravely lawn mower.

Before you work under your deck, confirm your ignition key has been removed and the spark plug wires are disconnected for safety. Wearing a good pair of gloves, grab a hold of each end of your mower blade and rock it up and down.

You will need to remove your spindle housing and check for bearing failure when you feel movement or hear a knocking sound. Replace a failed spindle bearing.

Mower Idler Tensioner Bracket or Spring is Worn

Wearing of the idler tensioner bracket and spring can happen over time. This is the bracket that holds your idler pulleys in line. The spring can become weak or break causing your belt to come off your Gravely.

The hole where your spring attaches can also contribute to your spring and the problem of adding vibration. Replace a worn bracket or spring.

Debris Interfering with Proper Tension

Debris can collect on top of your Gravely mower deck and interfere with the movement of your tensioner pulley. Your belt can become loose when sufficient tension is not kept on your belt causing it to vibrate and come off your Gravely mower.

It isn’t only important to keep the belt area of your mower deck clean and free of debris for performance reasons, it is also important for safety reasons as well.

Dry debris collected on the top side of your mower deck can catch on fire from the heat of the belt.  

Find out more details on cleaning your mower deck in my articles on cleaning your lawn mower and finding and fixing mower deck problems. A clean mower will not only improve performance, but it can also extend your mower’s lifespan.

Debris in the Grooves of Your Mower Pulleys

Check the grooves of your pulleys for any objects that have gotten caught in them. This could be a small piece of bark, stone, or even packed mud.

Any additional material collected in your pulleys causes the belt to stretch around this additional material. It can cause your Gravely belt to roll off your pulleys or snap.

Oil or Rust on Your Mower Belt

Your Gravely belt can become covered in rust or oil from rusty deck components or an oil leak on your mower.

Oil on your belt can cause your belt to slip off your pulley and come off the mower. Rust will prematurely dry out your belt causing it to be more likely to break.

It’s important to fix the cause of the oil leak or rusting problem before you replace your deck belt with a new one or you will run into the same problems. Mower belts are expensive so you don’t want to keep on replacing them if you can prevent it.

Identify your oil leak and make the necessary repairs on your Gravely. It’s a good idea to regularly check your engine oil level before each use so you can identify any oil leaks early and prevent engine damage.

Clean the rust off your pulleys and deck. If the rusting is bad on your pulleys, you should replace them.

In Summary

Gravely deck belts can be pricey so the longer you can make them last, the better. Here are a few items that can extend the life of your Gravely mower belt to keep it from prematurely wearing or breaking and coming off your mower:

• Clean your mower deck after each mowing to remove debris
• Check for rubbing on deck components
• Keep oil and rust from forming on your belt
• Periodically check your pulleys and spindle housings for bearing failure
• Fix or replace any damaged brackets or belt keepers