Why is One Side of My Mower Deck Lower than others?

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A perfectly manicured, lush lawn starts with an evenly-cutting mower deck. But over time, gradual wear and tear can cause the mower deck lower than the other.

The result? uneven, ragged-cut, and unhealthy grass. While frustrating, this common issue can be fixed with proper diagnosis and maintenance.

In the following article, we’ll troubleshoot the root causes of an uneven mower deck. You’ll learn how to spot the signs, inspect key components, and correct unlevel decks for smooth performance.

With a few adjustments and replacements, your machine will be cutting with precision again in no time. I’ll walk you through common problems like bent blades, debris buildup, and worn spindles that knock decks out of level.

You’ll be able to identify issues, prevent future imbalances, and restore a perfectly even cut across your entire lawn. Let’s get into the details so you can get back to mowing with confidence.

Common Reasons Why Mower Deck lower Than Other

Finding the source of an uneven and lower mower deck on one side is the first step toward leveling it out. In this section, I have addressed bent blades, debris buildup, damaged spindles, lift arm problems, and other common causes that would cause your mower deck to become lower on one side over time.

Bent Mower Blades

Mower blades often get bent from encountering objects like rocks, sticks, or other debris while cutting the lawn. Even a small bend in a blade can change the height on that side of the deck. Bent blades lead to poor grass-cutting quality on the affected side, such as ragged or scalped cuts.

Visually inspect blades regularly and check for even tip heights side-to-side. Replace any bent blades promptly to restore proper deck height and cutting. Keep spare blades on hand for quick swaps when needed after impacts. Always check and replace damaged blades before mowing again.

Trying to straighten a bent blade rarely works well. The metal deforms and loses its structural integrity. Simply install new, sharp blades to instantly get the deck back to level cutting. It’s cheap blade insurance that prevents bigger problems down the road.

Sharp mower blades also produce a cleaner cut and healthier grass growth. So regular blade sharpening or replacement improves cutting performance beyond just fixing deck height. Keep blades in top shape and swap damaged ones immediately for a level, precision cut.

Buildup Under the Deck

Over time, clippings, grass, and other debris can accumulate under the mower deck. This material buildup acts as a cushion, subtly raising the height on that side. Routinely wash the underside of the deck to prevent buildup.

Use a putty knife, brush, and compressed air to remove any stuck-on material before adjusting the deck height. Letting clippings accumulate leads to a progressively unlevel cut over time. Stay on top of cleaning the deck to avoid fighting thick clumps of clippings.

Buildup Under the Deck
Buildup Under the Deck

Don’t just look at the blades when inspecting the mower deck. Check under the deck as well. Built-up grass and debris are invisible until you peek underneath. A quick look and clean can reveal the issue and get the deck back to level.

Worn or Damaged Spindles

The spindles are shafts that allow the mower blades to rotate beneath the deck. If a spindle gets damaged from wear or corrosion, it can cause that side of the deck to sag. Signs of a worn spindle include excessive wobble or play in the blades on that side and squeaking or grinding noises.

Wiggle the blades to feel for any looseness. Check spindles for excessive rust, damage, or wobble. Replace any compromised spindles to prevent further deck issues. Don’t let a damaged spindle lead to bigger problems down the road.

Catch deteriorating spindles early before they allow the deck to sink lower on that side. Listen for grinding noises and wiggle blades to check for wobbles. Maintain spindles well for a long-lasting level cut.

Damaged or Collapsed Lift Arm

The lift arms on a mower deck raise and lower the deck for cutting height adjustment. If one side’s lift arm is damaged or loose, that side of the deck may not raise properly, causing it to sit lower.

Inspect the lift arms visually for damage and test that they raise each side of the deck evenly. Look for loose connections or broken parts. Tighten hardware or replace components as needed to get both sides moving correctly.

Lift arms take lots of wear and tear. Check them routinely for damage and looseness. Lubricate pivot points to keep arms moving freely. Don’t mow with damaged lift arms.

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Checking Signs of Uneven Mower Deck

Once you suspect one side of your mower deck may be lower, there are several important signs to check for confirmation. Thoroughly inspecting the deck, blades, spindles, and lift arms allows you to identify issues causing the deck to be lower on one side. This section will cover techniques for visually inspecting your machine and spotting problems leading to a lower mower deck.

Visually Inspect the Deck

Start by looking underneath the mower deck for obvious damage, wear, or debris buildup that could cause or indicate an unlevel condition. Check that the underside looks relatively even from side to side. An uneven underside can point to issues like bent blades or debris buildup causing a lower mower deck.

Then inspect the blades on each side for any visible bends, damage, or severely worn or rusted areas. Bent or damaged blades are a common cause of an uneven mower deck. Ensure the blades are still sharp and evenly balanced. Dull or unbalanced blades lead to uneven cuts.

Check along the full length of each blade carefully. Even small dings and bends can throw off the cutting height on that side and contribute to one side of the mower deck being lower. The underside should look clean and damage-free. A quick inspection can reveal issues.

Check Blade Heights

Use a tape measure to check the blade tip height on each side from the ground. Have an assistant hold the tip steady while measuring. The measurements should be equal or close if on flat ground. Any big variance indicates an unlevel mower deck needing adjustment.

Be precise when measuring blade heights. Slight differences add up to a noticeably uneven cut and one side of the mower deck being too low which can also cause Lawnmower Backfiring.

Account for any lawn slope by slightly adjusting the deck rake. A slope may require a subtle slant to compensate while leveling the mower deck. But measure first on a flat section before skewing for slope. Precise measurement is key.

Check Lawn Mower Wheel Heights

In addition to inspecting the mower deck, blades, and other components, also check the height of the lawn mower wheels. If one or more wheels is set lower than the others, it can cause that side of the mower deck to be closer to the ground.

Use a tape measure to compare the wheel heights on both sides. They should be equal from the ground up to the center pivot point of the wheel.

Having all mower wheels set to the same height helps keep the deck level as you push the mower across uneven ground. Don’t overlook wheel height as a factor influencing mower deck evenness. Uneven wheel height could lead to poor cutting performance or issues like lawnmower sputtering.

Lawn Mower Wheel Heights
Lawn Mower Wheel Heights

Inspect Spindles

Wiggle each blade up/down and side-to-side to check for any looseness or wobble indicating a damaged spindle, allowing one side of the mower deck to be lower. There should be minimal play-grab firmness to feel subtle looseness.

Also, listen as you spin each blade for any grinding or squeaking noises. These sounds indicate failing bearings or loose parts that can lead to an uneven mower deck. Ensure spindles are not excessively rusty or damaged. Solid spindle function is critical.

Replace deteriorating spindles early before they allow the mower deck to sink lower on one side. Don’t mow with damaged spindles; replace them promptly. Careful inspection and maintenance prevent issues.

Check the Lift Arms.

Raise and lower the deck while watching the lift arms on each side. See if one side seems slower or hangs lower, indicating an issue leveling the mower deck evenly. The arms should move in sync to keep the deck level.

Consult your owner’s manual for proper lift arm adjustment if needed. Make sure the pivot bolts are tight. Check for binding. Lubricate lift arm pivots as needed to prevent one side of the mower deck from ending up lower. Don’t ignore lift-arm issues.

Carefully checking for signs of unevenness in your mower deck gives you the information needed to troubleshoot and resolve deck height issues. Keeping your mower deck properly leveled through routine inspection and maintenance ensures smooth, precision cutting across your entire lawn.

4 Steps to troubleshoot mower deck lower than other

Following proper blade, debris, lift arm, and component maintenance practices allows you to keep your mower deck level side-to-side over time. Taking methodical action can help level a mower deck that is lower on one side for smooth, precision cuts. This section outlines a 4-step process for troubleshooting a lower mower deck condition.

Step 1: Sharpen or Replace the Mower Blades

The first step in leveling an uneven mower deck is to address any bent, damaged, or imbalanced mower blades. Bent blades need replacement, as they cannot be reliably straightened once deformed. Replacing blades can help raise a sagging side of the mower deck back to proper height if blade issues are causing the unevenness.

Keep extra sharp blades on hand so they can be swapped out when hitting obstacles that bend them and throw off the mower deck level. Sharp blades also produce cleaner cuts than dull blades, which can cut unevenly. Proper mower blade maintenance is key to preventing and fixing an uneven mower deck.

Sharpe Mower Blades
Sharpe Mower Blades

Step 2: Clear Clippings and Debris from Underside

Use a putty knife, brush, and compressed air to thoroughly clean the underside of the lawnmower deck. Remove all built-up grass clippings, leaves, dirt, and other debris that can raise one side of the mower deck over time. Even small amounts of material buildup under the deck can alter the cutting height.

Send any stuck-on grass and gunk flying with compressed air to get a completely clean underside. This allows for proper blade tip measurement and adjustment when leveling an uneven mower deck. Don’t try to adjust the deck without thoroughly cleaning it first.

Step 3: Adjust the Lift Arms

Check your mower operator’s manual for lift arm adjustment instructions if needing to get an uneven mower deck back to level. You may need to tighten hardware, lubricate pivots, remove obstructions, or tweak alignment to keep the deck level.

Ensure both lift arms raise each side of the mower deck evenly in sync. Any sloppy movement or sticking needs correction to prevent one side from ending up lower. Properly functioning and adjusted lift arms are critical for controlling the mower deck height and keeping it level.

Step 4: Replace Damaged Parts

If a spindle, pulley, lift arm, or other mower deck component is damaged beyond repair, it will likely need replacement when leveling the deck. Swap out any hopelessly bent or rusted parts not moving smoothly.

Add metal shims or spacers underneath to raise a sagging side of the mower deck that’s low due to worn components. Carefully bend deck brackets back into shape if slightly deformed. Severe damage may require full mower deck replacement.

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Regular Maintenance for Mower Deck Level 

Keeping up with routine maintenance is crucial for maintaining a level mower deck over the long run. If you let maintenance slide, small issues can compound and cause the deck to end up uneven side-to-side. Stay on top of basic care and inspection tasks to prevent and catch problems early.

Regular Maintenance for a Level Mower Deck

  • Sharpen mower blades frequently for optimal cutting performance
  • Wash the underside of the deck often to prevent debris buildup
  • Lubricate deck components so they move smoothly
  • Avoid hitting solid objects that can bend blades
  • Inspect and replace damaged parts promptly
  • Monitor the condition of spindles, pulleys, lift arms
  • Periodically check adjustments and level the deck
  • Address issues promptly to prevent bigger problems


Understanding the causes of a mower deck lower, like bent blades, debris buildup, worn spindles, and lift arm issues allows you to troubleshoot and fix it. Carefully inspect your deck, blades, and components. Make needed adjustments and replacements. Keeping your deck properly leveled results in a perfectly manicured lawn.


What is the best way to sharpen mower blades?

You can use a blade sharpening file or stone, or take them to a professional sharpening service for a precise and balanced result.

What kind of lubricant should I use for mower deck components?

Use a lightweight lithium-based grease or a multi-purpose oil for lubrication. Avoid heavier lubricants that can attract dirt and debris.

Can I prevent hitting objects while mowing?

Yes! Pay close attention to your surroundings, slow down in unfamiliar areas, and avoid mowing near obstacles like trees, rocks, or fences.

What tools do I need to adjust the lift arms on my mower deck?

Consult your mower’s manual for specific instructions and required tools. Most adjustments involve wrenches or sockets.

Is it worth replacing a damaged mower deck?

Evaluate the extent of the damage and cost of replacement compared to the mower’s overall condition and age. Minor damage might be fixable, but extensive damage or a very old mower might make replacement more logical.

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