Your lawn tractor is shaking so badly it feels like you are going to vibrate right out of the seat. Riding on your lawn tractor on uneven ground can bounce you around a bit, but adding a severe vibration can make using your tractor very uncomfortable.
A lawn tractor will experience vibration when the engine mounting bolts are worn or missing; the bearing in the clutch has failed; the mower blades are unbalanced; the deck belt is worn; the spindle housing or pulley bearings are bad; the idler bracket or spring is worn, or the debris is lodged in your lawn tractor.
I will share additional items that can cause a vibration in your tractor below. Keeping your lawn tractor clean and free of debris and regularly checking it to make sure all hardware is securely in place will help prevent vibration.
Follow the safety precautions in your owner’s manual before working on your lawn tractor.
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Follow all safety instructions provided in your equipment operator’s manual prior to 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.
8 Reasons for a Vibration in Your Lawn Tractor
Engine Mounting Bolts on Your Lawn Tractor
Engine mounting bolts are used to absorb the vibration from the engine. These mounting bolts, also known as motor mounts, are installed under your engine.
Over time these bolts can wear or break so they no longer are able to function correctly. Worn bolts will allow vibration from the engine to be felt throughout the lawn tractor.
Tighten any loose mounting bolts and replace bolts that are worn, broken, or missing.
Clutch on Your Lawn Tractor
Lawn tractors use an electric or manual engagement clutch. The electric clutch on your lawn tractor will cause a vibration when the ball bearing fails.
If you have a manual engagement clutch on your lawn tractor, check the bushings and linkages for failure. A manual engagement clutch is a type that is used with a belt and pulleys.
Mower Blades on Your Lawn Tractor
Lawn tractor mower blades can be the source of your vibration. Using the wrong blade or a blade that isn’t correctly balanced will begin to vibrate when it rotates at very high speeds.
Wrong-size lawn tractor blades:
I prefer to use OEM (Original Equipment Manufacturer) blades so I know I’m getting the correct high-quality blades. I’m not saying you should stay away from aftermarket blades.
The correct blades must be installed on your lawn tractor or you may experience vibration and potentially spindle housing damage. You must make sure your blade has the correct center hole size and blade length.
Understand that even with these measurements being correct, all aftermarket mower blades will not fit. It’s best to physically match up an aftermarket blade to an OEM blade to verify it’s a match.
One of the reasons why I stick with OEM blades is that I don’t want to deal with the hassle of trying to find a good match.
Unbalanced lawn tractor blades:
Blades that are not balanced will have a little wobble to them because one side of the blade weighs more than the other.
This can cause bearing damage to the spindle housing because of the movement in the blades. This movement at very high speeds will cause your mower deck to vibrate.
A mower blade can become unbalanced from uneven wearing. Dirt that swirls underneath the deck can wear the blade ends at different rates. Another way a blade can become unbalanced is by removing too much metal from one side of the blade during the blade sharpening process.
Find out more about sharpening and balancing your blades here.
Material Wrapped Around Your Lawn Tractor Blade Shaft
The mower deck can pick up foreign material that you may not have seen while mowing the lawn. While I recommend walking your lawn to pick up objects that can damage your lawn tractor, you still may miss some hard-to-see items.
Items such as string, wire, or even long sturdy weeds can wrap around the blade shaft. Inspect your shaft, also known as the spindle, and remove any items wrapped around it. Once this is done, check your spindle and housing for additional damage.
Bad Spindle Housing Components on Your Lawn Tractor
Bad bearings or a bent spindle in your spindle housings can cause your blades to wobble when you engage your blades causing vibration in your lawn tractor mower deck.
Before you check the spindle housing, put on a good pair of work gloves to protect your hands from the sharp edges of the mower blade. Next, grab a hold of each end of the blade and rock it up and down.
What you’re doing is looking for any movement. You may hear a knocking sound from the extra movement. If you feel movement, remove your mower blade and spindle housing. Inspect for bearing or spindle damage and replace the damaged items.
Deck Belt and Pulleys on Your Lawn Tractor
Your pulleys and mower deck belt may cause your shaking problem. When the belt is worn or has slack in it, it will not sit securely around the pulleys and may be loose or come off. Replace a worn belt if you find it is stretched, cracked, or has a glazed appearance.
If the belt appears in good condition, make sure your belt is routed around the pulleys correctly and the tension is adjusted to remove extra slack. Your belt may also not be sitting securely around the pulleys because the pulleys are not sitting parallel to the deck.
Check each pulley to make sure it is securely attached to the deck and doesn’t have a wobble to it.
You don’t want a lot of movement in the pulley where one side of the pulley sits higher off the deck than the other. When this happens, you most likely have a bad bearing on the pulley.
Find a failing bearing by slowly rotating each pulley by hand. Feel for a restriction and listen for bearing noise. If you experience either of these, your bearing must be replaced.
Note: Some pulleys will only use sealed bearings. In this case, you will have to replace the pulley and bearing assembly.
Idler Bracket & Spring on Your Lawn Tractor Deck
The idler bracket and spring can wear over time. The hole in the bracket can wear larger and the spring can stretch. A loose idler bracket and spring can make your lawn tractor vibrate.
Replace a worn idler bracket or spring. Check the bearing and bushing in the engagement linkage and replace if you find they are worn.
Debris Lodged in Your Lawn Tractor
Check your lawn tractor for small debris stuck in parts and small crevices of the tractor. When mowing the lawn, your lawn tractor kicks up the debris that can collect on your tractor. Something as small as a wood chip can cause extreme vibration.
Remove your spindle covers and clean off your deck regularly. Debris can collect under your pulleys and cause them not to sit flat and parallel to the deck. Vibration is created when your mower deck moves around the pulley that doesn’t sit flat on the deck.
Still Having Problems with Your Lawn Tractor?
You can encounter many different types of problems with your lawn tractor as it ages. I have put together a guide to help you quickly identify the causes and solutions for the type of problem you are encountering.
I cover common problems like a lawn tractor not starting, smoking, cutting uneven, vibrating, dying after running, and more.
Check out my guide: Common Lawn Tractor Problems & Solutions.
If you encounter a problem you don’t feel comfortable troubleshooting or repairing, contact your local lawn tractor dealership or repair shop for assistance.