Riding Mowers & Tractors: Why does my riding mower deck vibrate?

If the mower vibrates when you engage the cutting blades, there might be a problem with the blade drive system. Deck vibration can be caused by an unbalanced blade, worn pulley or mandrel, bad blade belt or debris caught inside a pulley.

Loose nuts or bolts on the pulleys, mandrels or blades can also cause vibration. Remove the mower deck and re-tighten all fasteners.

Check for wear on pulleys, mandrels and blades. Replace any worn or damaged components.

riding mowers & tractors

THESE REPAIRS MAY HELP SOLVE YOUR RIDING MOWERS & TRACTORS PROBLEM

JC-RM-Replace-the-riding-mower-mandrel-assembly

Replace the riding mower mandrel assembly

The mandrel assembly attaches to the deck and spins the blade to cut grass. A blade won't move if the mandrel locks up. A damaged mandrel causes mower deck vibration and uneven cutting. Examine the mandrels regularly and replace any damaged mandrels.

Riding mower mandrel assembly

Find the required part specific to your product.

RG-RM-Replace-a-Riding-Mower-Mandrel-Assembly-Intro-Image
March 1, 2017By Lyle Weischwill

How to replace a mandrel assembly on a riding lawn mower

If the blade shaft on your riding lawn mower vibrates or won't spin the blade, the mandrel might be worn or damaged. This DIY repair guide and vidoe explain how to replace a riding lawn mower mandrel assembly in just 6 steps.

Repair difficulty
Time required
 30 minutes or less
JC-RM-Replace-a-riding-mower-blade

Replace a riding mower blade

A bent mower blade won't cut grass evenly and may cause mower deck vibration. Dull blades leave ragged edges on cut grass. Inspect mower blades regularly and replace a riding mower blade if it's damaged, bent or dull.

Replace a riding mower blade

Find the required part specific to your product.

RG-RM-Replace-a-Riding-Mower-Blade-Intro-Image
January 1, 2015By Lyle Weischwill

How to replace a riding lawn mower blade

If brown, tattered grass tips make your lawn look sick, one or more blades on your riding mower could be dull or bent. This repair guide and video show how to replace a riding mower blade in 30 minutes or less.

Repair difficulty
Time required
 30 minutes or less

RG-RM-Replace-a-Zero-Turn-Riding-Mower-Cutting-Blade-Intro-Image
January 1, 2015By Lyle Weischwill

How to replace a cutting blade on a zero-turn riding mower

If your grass looks tattered after mowing with a zero-turn riding, the problem could be a dull or damaged blade. This easy-to-follow repair guide and video explain how to replace a blade on a zero-turn riding lawn mower.

Repair difficulty
Time required
 15 minutes or less
JC-RM-Replace-the-riding-mower-blade-belt

Replace the riding mower blade belt

The blade belt spins the blades to cut the grass. A worn or broken drive belt won't spin the cutting blades so your mower won't cut the grass. A worn blade belt can also cause mower deck vibration or uneven cuts. Examine the blade belt regularly and replace it if it's worn or broken.

Riding mower blade belt

Find the required part specific to your product.

RG-RM-Replace-a-Zero-Turn-Riding-Mower-Blade-Belt-Intro-Image
January 1, 2015By Lyle Weischwill

How to replace the blade belt on a zero-turn riding mower

If the blades won't spin on a zero-turn riding mower, the problem could be a broken blade belt. Replace a broken or worn blade belt on a zero-turn riding lawn mower by following the steps in this DIY repair guide and video.

Repair difficulty
Time required
 30 minutes or less

RG-RM-Replace-a-Riding Mower-Blade-Drive-Belt-Intro-Image
January 1, 2015By Lyle Weischwill

How to replace a riding lawn mower blade drive belt

If the blades on your riding lawn mower don’t spin fast enough—or don’t spin at all—the blade drive belt could be worn out or broken. This repair guide and video show how to replace a blade drive belt in less than an hour.

Repair difficulty
Time required
 45 minutes or less
JC-RM-Replace-the-riding-mower-deck-idler-pulley

Replace the riding mower deck idler pulley

The deck idler pulley tightens the blade belt against the blade pulleys to spin the blades when you shift the blade engagement lever to engage the blades. You might need to replace the riding mower deck idler pulley if the blades don't spin. A worn idler pulley can also cause uneven cuts and mower deck vibration, so check the idler pulley if you notice these symptoms. Replace the deck idler pulley if it's worn or broken.

Riding mower deck idler pulley

Find the required part specific to your product.

Symptoms common to all riding mowers & tractors

Choose a symptom to see related riding mower and lawn tractor repairs.

Main causes: punctured tire or inner tube, leaky valve stem, damaged wheel rim
Main causes: worn or broken ground drive belt, bad seat switch, transaxle freewheel control engaged, transaxle failure, dirty carburetor
Main causes: shift lever needs adjustment, neutral control needs adjustment
Main causes: worn or broken blade belt, broken belt idler pulley, blade clutch cable failure, bad PTO switch, damaged mandrel pulleys
Main causes: damaged cutting blade, worn deck pulley, damaged mandrel pulley, loose fasteners on mower deck components
Main causes: engine overfilled with oil, leaky head gasket or sump gasket, damaged carburetor seals, cracked fuel pump, broken fuel line
Main causes: clogged carburetor, damaged flywheel key, dirty spark plug, stale fuel, improper valve lash, engine needs a tune up
Main causes: faulty battery, bad alternator
Main causes: unlevel mower deck, dull or damaged cutting blades, worn mandrel pulleys, bent mower deck, engine needs tune up

Repair guides common to all riding mowers & tractors

These step-by-step repair guides will help you safely fix what’s broken on your riding mower or lawn tractor.

January 1, 2015
By Lyle Weischwill
How to replace a riding lawn mower rear tire

Your mower can’t run on a damaged rear tire. Here’s how to install a new one.

Repair difficulty
Time required
 60 minutes or less
January 1, 2015
By Lyle Weischwill
How to replace a riding lawn mower blade

If a blade on your mower is dull or bent, replace it following the steps in this repair guide.

Repair difficulty
Time required
 30 minutes or less
January 1, 2015
By Lyle Weischwill
How to replace a riding lawn mower fuel filter

Help your mower run better by replacing the fuel filter during your riding mower's annual tune-up.

Repair difficulty
Time required
 15 minutes or less

Articles and videos common to all riding mowers & tractors

Use the advice and tips in these articles and videos to get the most out of your riding mower or lawn tractor.

August 6, 2020

How to remove a lawn mower blade using a removal tool

By Sears PartsDirect staff

Learn how a blade removal tool makes replacing the blade easier and safer

April 9, 2019

Riding mower parts and supplies to stock up on video

By Sears PartsDirect staff

Keep these 6 things on hand to keep the mower season running smoothly.

January 1, 1970

How to tell if a fuse is blown

By Lyle Weischwill

Learn how to tell whether a fuse is blown