Toro Mower Making Grinding Noise – Why And What To Do?

A grinding noise coming from your Toro lawn mower can be annoying and indicate that there is a problem with your machine. We researched to find out what these problems are and how to fix them.

Before you attempt to troubleshoot or repair your Toro lawn mower, you need to know why it's making a grinding noise. Here are the common reasons and their corresponding solutions: 

  • Worn bearings: You should lubricate the bearings. If there's visible damage, replacement may be needed.
  • Bent crankshaft: Straighten or replace the crankshaft.

Keep reading to learn more about the underlying issues causing your Toro lawn mower to produce a grinding noise. Included are details on fixing these problems. Also, find out the best lubricant to use and some of the repair costs. 

How To Fix Toro Lawn Mower Producing A Grinding Noise

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A lawn mower making unusual noises doesn't necessarily mean it has a problem. It's normal for riding mowers or lawn tractors to produce a grinding sound.

Your push lawnmower can produce the same sound if you push it when the drive is detached. However, a sudden grinding sound that wasn't there before is a sign your machine has a problem.

Cleaning and lubricating the affected parts may be all you need to do to eliminate the noise. But, if the noise persists, you need to find out what is wrong. 

Some of the most common reasons your lawn mower is producing a grinding sound include the following:

Worn Bearings

The bearings in the mandrel assembly of your riding lawn mower go through normal wear and tear. The mandrel is the component under the deck that holds the blades in place. The bearings can overheat and dry, so you must lubricate them regularly.

You can find this set of mandrel bearings on Amazon.

When the bearings are worn, they can produce strange noises, including a grinding sound. If not replaced promptly, your blades could drop down from under the deck.

A broken seal can allow dirt to interfere with the normal movement of the bearings, which can also produce strange noises. You can find out if this is the problem by shaking the blade.

But first, ensure you shut down your mower and park it somewhere safe. If the blade plays excessively, you will have to replace the bearings.  Afterward, check the mandrel for any damages. Unless there is visible damage, there’s no need to replace it.

Check out this mandrel assembly on Amazon.

Bent Crankshaft

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The crankshaft of a push lawnmower can bend if the blade hits a rock or stump with so much force that it causes jamming against the bearing. As a result, it may overheat, produce smoke, and make a grinding noise. 

To check if this is what happened, unplug the spark plug wire and remove the spark plug. This is to ensure that your mower will not start accidentally.

Also, tie the brake handle using a rope or a pair of clamps, or ask someone to hold it for you. Next, flip your mower over, ensuring the air filter is facing up. 

Pull the pull-start that you normally start your engine with. In this instance, the engine will not start, but the crankshaft will spin. If the bolt that connects the blade to the crankshaft wobbles, then it is bent. You can straighten or replace it.

Check out this video for a demonstration of how to check if the crankshaft is bent.

How To Straighten A Bent Crankshaft 

Some lawn mower experts recommend using a long, heavy-duty pipe instead of a hammer to straighten the crankshaft. This is because you might damage the crankshaft or adjacent parts during the process.

As in the previous section, you will need to remove the spark plug and hold the brake handles using a pair of clamps. Turn the mower over with the air filter facing up. 

Check out this dial indicator on Amazon.

Next, measure the gap between the deck and the crankshaft all around. There are several ways of doing this.

You could use a dial indicator like the one shown above, but ensure you follow the instructions in the manual. For this post, a strong magnet and a straight tool are used.

The steps to straighten the crankshaft include:

Measure The Gap Differences Around The Crankshaft 

  1. Place a magnet on the deck.
  2. Place one end of the straight tool on the magnet and the other end as close as possible to the crankshaft. 
  3. Pull the pull-start and turn the crankshaft until the gap between the crankshaft and the deck is the widest. Measure this distance.
  4. Again, pull the pull-start and turn the crankshaft. Mark this side with the lowest gap and measure the distance.
  5. Your goal is to have an equal gap all around the shaft between the crankshaft and the deck, so continue to the next few steps.

Straighten The Shaft

  1. Take your mower outside, place it on flat ground, and turn it over. Remember that the air filter should face up.
  2. Turn the shaft so that the side with the mark faces the front of the mower.
  3. Place your right foot on the deck and firmly grip the brake handles with your left hand. 
  4. Place the pipe over the crankshaft so that it enters the hole in the pipe. 
  5. Pull the pipe backward with your hand to adjust the crankshaft's position. 
  6. Check the gap on the side you marked the crankshaft. You should have adjusted it a little so that the gap is wider. 
  7. Turn the shaft to the opposite side of the mark, and repeat the procedure. 
  8. Keep repeating until you achieve an equal gap all around the shaft.

Check out this video for a demonstration of the process.

If you still cannot straighten the crankshaft, you should replace it. Keep in mind that this option can be expensive. You might have to buy a new mower instead. You'll need to consult with your dealer to find out more about this and make a decision.  

You will likely need to repair or replace the blades. After hitting against a hard object like a rock, they could have also bent. As a general principle, most manufacturers recommend that you replace the blades when damaged.  

Check out this Toro lawnmower blade set on Amazon.

How To Maintain Your Mower 

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Lawnmowers go through normal wear and tear, and at some point, you will have to replace some parts. Eventually, you may need to buy a new lawnmower.

To prevent your mower from producing strange sounds, including a grinding noise, you should lubricate it often. The best lubricant is the one recommended by the manufacturer of your lawn mower.

To lubricate the bearings and other moving parts of your Toro lawn mower, you can use a general-purpose lithium complex no. 2 lubricant. 

Remove debris and other objects that may damage your mower, causing it to produce unusual sounds. This will also prevent potential harm to you and those around you.

The blades move at high speeds and propel objects out of the discharge chute at 2oo miles per hour. 

Don't forget to mark pipes or other immovable structures that you may damage with your mower or that may damage your mower. 

Check out this general-purpose lithium grease on Amazon.

How Much Does It Cost To Repair A Lawn Mower?

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The cost of hiring a professional to repair your lawn mower will vary based several factors, such as the type of mower and how it is powered.

In general, the cost to repair a push mower starts from $40, while that of repairing a riding mower starts from $140.

A lawnmower company can charge you a flat rate, but others may charge you an hourly rate. On average, they charge $55 per hour but can range from $45 to $100 per hour. 

In Closing

Professional lawn mower with worker cutting the grass in a garden

You should never ignore any sudden strange noises that emanate from your Toro lawn mower. Grinding sounds are one of them.

The sound can signify that something is wrong. The mower may have worn bearings or a bent crankshaft. We discussed solutions to these problems in this post.

To ensure your Toro lawn mower remains in good condition, lubricate the moving parts regularly. Also, before using your mower, clear your lawn of any objects and debris. 

If you enjoyed reading this post, check out these related articles:

How To Start A Toro Lawn Mower With A Choke [Step By Step Guide]

Lawn Mower Smoking Leaking Oil

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