Cub Cadet Mower Deck Problems (7 Steps to Find & Fix)

You may not regularly inspect the mower deck. Doing this may leave you with a costly repair if you wait until you start hearing a noise or begin to smell burnt rubber.

These early indications can signify Cub Cadet mower deck problems:

• Tips of your grass appear brown a couple of days after you mow
• The cut of your lawn is uneven
• Uncut strips of grass
• The Mower deck falls off
• Deck begins vibrating

4 most common Cub Cadet mower deck problems:

• Uneven cut
• The belt keeps falling off or breaking
• Deck is Vibrating
• Blades won’t engage

Read on and I’ll explain how to find and fix your Cub Cadet mower deck problems. You’ll find links to articles in more detail.

Always remove the spark plug wire and ignition key before starting any deck troubleshooting and repairs. Wait for all parts to stop moving. Wear safety gear.

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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.

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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.

Common Cub Cadet Mower Deck Problems

1. Bad or Uneven Cut

The mower blades create air movement under the area of the deck to form a suction. This suction lifts grass while the blade passes by to give it a nice cut.

When you no longer achieve a good cut, first check the tire pressure. If you have a low tire, your mower deck will no longer sit level.

Once you have verified the tire pressures are right, check the condition of the mower blades and deck components for wear or damage.

Detailed information can be found at:
Reasons a Cub Cadet Has a Bad or Uneven Cut

Cause	Solution
Mower blade is dull or worn	Sharpen a dull blade. Replace if the sail is thinner than the center of the blade, the end of the blade is rounded, or the blade has gouges.
Mower blade is bent	Replace a bent blade. Do not attempt to straighten it.
Mower blade is installed wrong	Install the blade with the correct hardware. The blade sails must point upward toward the deck.
Mower deck is plugged with grass	Scrape the deck to remove grass clippings.
Tire pressure is low	Correct the tire pressure. Make sure the left and right tire pressures are equal.
Mower deck isn’t level	Level the deck using the instruction in the operator’s manual.
Blade spindle is bent / Spindle housing bearing damage.	Replace a bent spindle. Check the spindle bearing and replace it if worn or damaged.
Worn deck belt	Replace a stretched, worn, cracked, or shredded belt.
Bad pulley bearing	Replace a bad pulley bearing restricting pulley rotation or making the pulley wobbly.
Engine speed is too low	Always run the engine at full throttle when engaging the blades.
Ground speed is too fast	Slow down and mow according to the conditions. Slow down when cutting thick, tall, or wet grass or when operating on inclines.
Incorrect overlapping path / grass is too tall	Properly overlap your paths so you don’t leave strips of grass. Double or triple-cut grass when it is very tall.
Mower deck shell is damaged	Attempt to straighten the deck if possible. Replace the deck shell or complete deck assembly if it is not.
Lawn is uneven	Level an uneven lawn using a lawn roller to avoid scalping. Use a small format mower for ditches.

2. Mower Deck Belt Keeps Falling Off

The deck belt keeps falling off your Cub Cadet mower when deck components are worn, debris is stuck in the deck components, or the belt is worn or damaged.

When proper tension isn’t able to be placed on the belt, the belt can become loose and come off the pulleys.

Detailed information can be found at:
Cub Cadet Belt Keeps Falling Off or Breaking

Cause	Solution
Stretched or worn mower deck belt	Replace a stretched or worn mower deck belt.
Belt keeper is damaged	Attempt to bend the keeper back to its original position. Replace a damaged belt keeper.
Deck belt is shredded	Replace a shredded belt. Find and fix the item the belt is rubbing against. Make sure the belt is routed around the pulleys correctly.
Bad pulley bearing	Replace a bad pulley bearing or pulley assembly that is restricting pulley rotation or making the pulley wobbly.
Bad spindle housing bearing	Replace a bad spindle housing bearing or spindle housing assembly.
Idler tensioner bracket or spring is worn	Replace a worn bracket or spring.
Debris is interfering with proper tension	Remove debris collecting around and under the tensioner. Make sure the tensioner is able to move.
Debris buildup in the pulley grooves	Remove debris collecting under the pulleys or in the pulley grooves.
Oil on your deck belt	Fix an oil leak. Remove oil from the mower deck and components. Replace with a new belt.
Rust on your deck belt	Remove rust from deck components. Replace any components that are extremely rusty. Replace the mower deck belt.

3. Mower Deck is Vibrating

You’re feeling more vibration than normal and it’s coming from your Cub Cadet mower deck. A common reason for this is unbalanced mower blades.

Blades can become unbalanced, with one side of the blade heavier than the other, from normal wear or during the blade sharpening process.

You may also find failed bearings in the deck components, a loose belt, a worn clutch, or debris lodged in the mower deck.

Detailed information can be found at:
Reasons a Cub Cadet Mower is Vibrating

Cause	Solution
Clutch is worn	Replace an electric clutch with ball bearing failure. Check the belt, pulley, bushings, and pulleys for failure on a manual engagement clutch.
Mower blades are installed wrong	Install the blade with the correct hardware. The blade sails must point upward toward the deck. Tighten the nuts to the specification listed in your operator’s manual.
Mower blades are unbalanced	Balance the blade so they are of equal weight on each end of the blade. Remove a little metal for the heavier end until the blade is of equal weight.
Foreign material is wrapped around the blade shaft	Remove any material that has wrapped itself around the blade shaft. Inspect the spindle housing for damage.
Bad bearing in the spindle housing	Replace a bad spindle housing bearing or spindle housing assembly.
Deck belt is loose or stretched	Replace a stretched, worn, cracked, or shredded belt.
Bad pulley	Replace a bad pulley bearing or pulley assembly that is restricting pulley rotation or making the pulley wobbly.
Debris lodged in the mower deck	Inspect the mower deck and remove any debris and foreign objects.

4. Blades Won’t Engage

Blades won’t keep rotating under the deck when the belt is worn and no longer grips the pulleys to turn the blades.

You will also need to check for items that can fail to engage the clutch solenoid on an electric clutch or a worn clutch cable, linkages, and bushings on a manual clutch.

Detailed information can be found at:
Cub Cadet Mower Blades Won’t Engage or Turn On

Cause	Solution
Mower deck belt is worn	Replace a stretched, worn, cracked, or shredded belt.
Belt has come off the pulleys	Look for a worn tensioner arm or spring, loose belt, or worn pulley bearings.
PTO switch is faulty	Replace the PTO switch.
Clutch is Bad	Replace a bad electric clutch.
Clutch cable or linkages are worn on a manual clutch model	Replace a worn clutch cable, bushings, or linkages on a manual clutch.
Battery is weak	Charge a weak battery. Replace a bad battery that is no longer able to hold a charge.
Safety switch is bad	Replace a bad safety switch.
Fuse is blown	Replace a blown fuse with the same capacity fuse. Have a mechanic find the root cause if the mower continues to blow a fuse.

7 Steps to Find & Fix Cub Cadet Mower Deck Problems

When addressing Cub Cadet mower deck problems, start with the simple items and work your way toward the more complicated mower deck issues. These steps apply to Cub Cadet’s zero-turns and riding mowers.

1. Remove Spark Plug Boot and Ignition Key

Before proceeding with these steps, it is necessary to take precautions to ensure your safety. Working with any powered machine can be extremely dangerous.

Follow these guidelines along with consulting your owner’s manual for additional safety tips.

• Make sure your Cub Cadet’s engine is off and the key is removed from the ignition
• Disconnect the spark plug boots off the spark plug to prevent the engine from starting
• Wear heavy-duty leather work gloves to protect your hands from the mower blades

Do not start working on your Cub Cadet until all safety precautions have been taken and all moving parts stop.

2. Check the Condition of Your Mower Blades

The tops of the grass will provide you with a dead giveaway your blades are dull and it is time to sharpen or replace them.

What do I mean by this? Right after you get done mowing, your grass will look pretty good. The day after your lawn was mowed it may have a brown or burnt look to it.

Go out to your lawn and pull up a blade or two of grass. Look at the tips of them and you will see the blades are brown, have little cuts, or are shredded.

This is actually a bruised piece of grass where the grass was beaten and not cut.

Your blades must be replaced if you notice bruised grass. If your blades are only dull and in good condition, you can remove the blades and sharpen them.

Bent mower blades can also affect the cut of your lawn. With your Cub Cadet mower parked on a flat surface, measure from the ground to one blade tip and then spin the blade 180 degrees and measure the opposite blade tip. If there is over and 1/8″ variance, replace with a new blade.

Never attempt to straighten an Cub Cadet blade. Repeat this step with other blades under your mower deck. I go into more detail on sharpening, replacing, and balancing blades here.

3. Check Your Tires for Low Air Pressure

If your blades are in good shape and there is no more bruising of the grass, but you notice uneven cuts in the yard, you need to check your Cub Cadet’s drive tires. The drive tires are the large tires on the rear of the mower.

Make sure your Cub Cadet’s tire pressures are to the manufacturer’s recommendation. A soft tire can make your mower deck not sit level resulting in an uneven cut due to one side of the mower decking sitting higher than the other.

4. Mower Deck Height Must Be Level

If your lawn mower tires are set to manufacturer specification, the next step to perform is to check the deck height. Make sure your Cub Cadet mower is parked on a flat surface.

Measure the deck height on all four corners of the mower deck to ensure the measurements are all the same. If they are not, make adjustments according to your owner’s manual.

The front of a zero-turn deck may be required to sit slightly lower than the rear. Consult the manual for exact specifications.

Leveling the deck can be a little tricky and sometimes can take a trained dealer up to two hours to adjust. If you have a hard time making the adjustment, you can have your local Cub Cadet dealer take care of it.

5. Check the Spindle Housing Bearing

If your deck is level and you still have a bad cut, you need to check your Cub Cadet mower deck bearing(s) under your deck.

Again, check to make sure the spark plug boots are off the spark plugs for safety. Some small engines will have one spark plug while others have two.

Making sure the spark plug boots are removed will prevent the engine from starting. Be very careful and put on a good pair of leather work gloves to protect your hands.

Grab a hold of one Cub Cadet blade at a time at each end of the blade and see if you can rock the blade up and down. Feel this motion and listen for a nock.

If the blade moves or creates a noise, you have a bad bearing in the spindle housing, or a quill assembly, as they are sometimes called.

You have to make a decision whether you are able to rebuild it or if it is just easier for you to replace the cutter housing assembly which typically includes the bearing.

6. Check the Mower Deck Belts

Now we know your blades, tires, deck level, and deck bearings are all okay, but your yard still looks bad.

It is time to look at the Cub Cadet deck belts and the pulleys the belts run on. So if your belts have a shiny or glazed look to them on the edges, you need to replace them.

7. Check Deck Pulleys & Idler Pulley Brackets

Look at the Cub Cadet pulleys and idler pulley brackets. To check your pulleys, with the mower deck belt off, spin them to feel they move smoothly and listen for noise.

If there is any noise or any restriction when moving the pulley, the pulley needs to be replaced. Check the idler pulley bracket to make sure there isn’t any play where it mounts to the deck. Any movement will require a new pulley bracket.

If your Cub Cadet idler pulley bracket has not been greased in a while it may not move as it was designed to do. The bracket needs to have movement so you can turn the blades on and the instant load won’t snap the Cub Cadet deck belt.

To prevent the belt from breaking, the idler pulley bracket is designed to move and spring back to put tension back on the belt.

If the bracket is unable to move, the belt can slip and cause the blades to also slip in heavy or deep grass so our cut looks bad the next day.

Some of the idler brackets will have a bushing installed in them while others may use bearings. The bushings will be either plastic or brass.

This idler pulley bracket may have a grease zerk on it. If yours does not, you may need to take it apart, grease it up and put it back together so it has movement once again.

Keep the idler bracket greased when doing your routine maintenance checks throughout the mowing season.

Grass Stuck Under Cub Cadet Deck Can Affect Quality of Cut

You need to keep in mind that grass stuck under your deck can disrupt the quality of the cut also. You may not think scraping your Cub Cadet deck is that important, but it really is.

You have to remember the depth of the deck gives us an area to stand grass up so the blades can pass by and create a nice cut.

If the grass plugs up this space you lose under the deck will cause you to lose the lift of the grass created by the movement of the blades.

Many people ask if there is a way to keep grass from sticking to the bottom of the Cub Cadet deck. You’ll never be able to prevent grass buildup under your deck altogether, but here are a few ways to reduce the amount of grass sticking to your mower deck:

• Always run your Cub Cadet mower at full throttle
• Avoid cutting wet grass
• Regularly cut your lawn so the grass doesn’t get too long and result in clumping of grass
• Coat the underside of your Cub Cadet deck with a Teflon or silicone spray designed for your lawn mower deck

How Often Should You Perform Cub Cadet Mower Deck Maintenance?

The lawn mower deck is a main component of the mower, but I think it is often the most neglected. 

For the average homeowner, Cub Cadet mower deck maintenance should be performed at least twice per mowing season. If your yard is heavily watered or fertilized you need to perform maintenance more often.

The grass is full of moisture and fertilizers, if you use it, that can create erosion of the deck so you may not get the life you expected out of your Cub Cadet mower deck. Scrape and clean out the undersides of your decks more than once a year.

While you are under the deck, use the steps above to identify all mower deck parts are functioning as needed and are in good condition. Performing these routine checks will help you prevent more costly repairs.