I have been in your situation with a zero-turn mower that begins to shake excessively. It can seem like your mower is just going to fall apart from all the vibration. There are many items in your deck and zero-turn that can wear or fail to cause your zero-turn to shake.
A zero-turn mower can begin vibrating when the hardware is worn or loose and no longer securely holds components in place. The vibration can be caused by a failing clutch; loose linkages; unbalanced blades or bad bearings in the spindle housings or pulleys.
I have found something as small as a wood chip lodged under my pulley causing vibration. To help you find your problem, I have listed common problems that can develop in a zero-turn and cause it to shake.
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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 Zero Turn Mower is Vibrating
Before you begin working on your zero-turn lawn mower, it’s important to take proper safety steps to prevent injury. This includes:
- Remove the key from your ignition
- Disconnect the spark plug boots
- Set your parking brake and use wheel chocks to prevent movement
- Use jack stands to securely lift and access the underside of your mower deck
- Wear work gloves and safety glasses
- Refer to your operator’s manual for further safety instructions for your zero-turn model
Zero Turn Mower Engine Mounting Bolts
While your engine is running, it naturally shakes. Because of this, special engine mounting bolts are used under the engine to absorb some of the vibrations.
Some refer to the mounting bolt as a motor mount. Look at each bolt. Any mounting bolt that is worn, broken or missing must be replaced.
Zero Turn Mower Clutch
A clutch can fail resulting in a vibration being sent through the mower. Your zero-turn may use an electric clutch or a manual clutch. In an electric clutch, the ball bearing can fail. In a manual engagement clutch, bushing and linkage failure can contribute to the shaking of the mower.
Zero Turn Mower Blades
Vibrations can be sent through your mower due to several different mower blade issues. Incorrect blade installation, using the wrong mower blades, or unbalanced blades can all contribute to the problem.
Wrong mower blades
Zero-turn mower blades are not all the same. Besides having different styles of mower blades including high-lift, low-lift, gator, and mulching blades, there are different-sized blades.
For example, you can find many 52” mower blades that fit a 52” mower deck. While there are many blades, they will not all fit your model 52” deck.
I choose to buy OEM (Original Equipment Manufacturer) blades so I don’t have to mess around with making sure the blades are the right size and fit securely to my zero-turn. OEM blades are good quality mower blades.
There are some good quality aftermarket blades including Stens and Oregon blades. You need the measurements for both your blade length and center hole size.
You do have to be careful when purchasing blades because the measurements listed may match the measurements you need, but the blade is still wrong.
If you choose to use aftermarket mower blades, match them up to an OEM blade to confirm they will work on your mower.
Incorrect mower blade installation
Install your mower blade with the hardware required by your mower manufacturer. Not using the correct hardware or installing it in the wrong order can cause your blades to not sit securely on your mower.
A slight movement in your mower blades becomes a big vibration problem when your blades begin rotating at high speeds.
Refer to your zero-turn owner’s manual or your manufacturer’s parts diagram to confirm you are using the correct hardware and it is installed in the right order. If your zero turn uses concave washers, make sure the cupped side is placed toward your mower blade.
Unbalanced mower blades
When your blades are not balanced, your deck will shake. The vibration can be so great, you feel like you’re going to shake right out of your operator’s seat.
A blade is unbalanced when the weight on one side of the blade is heavier than the other end. The uneven weight causes the blade to wobble when it turns which becomes more pronounced when it spins at high speeds.
A blade can become unbalanced from unequal wearing. Dirt is wearing one side of your blade more than the other.
It can also become unbalanced during the blade sharpening process when more metal is shaved from one side of the blade over the other. The balance is thrown off causing a vibration.
Not only does running an unbalanced blade cause vibration problems, but it can also cause spindle housing bearing damage and possible engine damage. Use a blade balancer to check your blade balance.
This is a relatively inexpensive tool that can save you from a larger expense due to blade damage. Read more about sharpening and balancing your zero-turn mower blades here.
Foreign Material around Your Zero Turn Blade Spindle
Wire, string or long weeds can get wrapped around the blade spindle, also known as the blade shaft. Check the spindle for foreign material and remove any that you find. Check for additional damage to the spindle housings.
Bad Zero Turn Spindle Housing Bearings
Bearings can go bad in your spindle housings from normal wear, unbalanced blades, or damage from blade impact. Bad bearings will cause blade movement that will cause a significant vibration when your deck is engaged.
With a good pair of thick work gloves, check for bad spindle bearings. Grab each end of the blade and rock the blade up and down. Listen for a knocking sound and feel for any movement.
If you notice either of these signs, disassemble your spindle housings and check for damage. Proceed with checking any other spindle housings.
You may be able to replace the bad bearing in your spindle housing. Depending on your zero-turn model, you may have to replace the whole spindle housing assembly. This may be because your manufacturer uses a spindle housing with a sealed bearing.
Zero Turn Pulleys
Bearings in your pulleys can wear and go bad on your zero-turn. This may cause a pulley to not sit flat and parallel to the deck.
When this happens, vibration is caused when your mower deck belt runs around the pulley that is not sitting securely on the deck. Check the bearing in each pulley to ensure it is good by slowly rotating the pulley by hand.
Feel for any resistance or bearing noise. Replace a pulley that has these symptoms or the pulley isn’t sitting securely on the deck and you notice extra movement.
Zero Turn Deck Belt, Idler Bracket and Tensioner Spring
When a belt is worn or stretched, it can have a lot of slack in it causing a vibration. Check your belt for signs of wearing including a glazed appearance, cracking, or shredding. Replace your belt with a new zero-turn deck belt when you find these conditions.
A worn idler bracket and tensioner spring can cause extra movement and vibration. The hole in the bracket can wear and become larger and the spring can become stretched, break or go missing.
Worn or Missing Components on Your Zero Turn
Parts can become worn or go missing causing components to not sit securely in place. Check over your zero-turn mower and deck for any missing or loose hardware. Tighten or replace parts to prevent your mower from rattling.
Debris Lodged in Your Zero Turn Mower
Even the smallest items can collect in your zero-turn and cause a vibration. It could be a small wood chip, stone, acorn, or another item that can lodge in your mower.
Check every spot on your mower including under your pulleys. Remove any extra items that have been collected in your mower.
Prevent vibration in your zero-turn by following these simple tips:
- Clean the dirt and debris from your zero-turn after each mowing.
- Regularly check, sharpen and install new blades when required. Check the bearings in your spindle housings and pulleys when changing your blades.
- Install correct and balanced mower blades.
- Check your mower periodically for loose or missing hardware.
Still Experience Problems with Your Zero Turn Mower?
Many different types of problems can develop in a mower. It doesn’t matter what brand you own.
While some mowers are built with stronger materials, bigger filters, better engines, and tougher spindle housings, they are all going to break down and cause issues at some time. Some may just not develop problems as quickly as others.
I put together a guide with common things that go wrong on zero-turns. In this guide, you will find a list of causes and solutions for a mower dying, smoking, vibrating, not starting, having cutting issues, and more.
Check out my guide at Common Zero Turn Mower Problems: How to Fix Them
If you still can’t find the solution to your problem or you don’t feel comfortable troubleshooting or repairing your mower, it is best to have an experienced mechanic check out your mower.
You can visit your local dealership that provides repair support for your brand mower. You may also find a lawn mower repair shop with experienced small engine mechanics.