Symptoms
- Metallic grinding or scraping sound while running
- Clanking that changes with engine speed or ground speed
- Noise gets worse over time or under load
- May be accompanied by vibration
Likely causes
- CommonDebris caught against the blade or deckA rock, stick, or wire can lodge against the spinning blade and grind.
- CommonWorn or misaligned drive beltOn self-propelled or riding mowers, a fraying belt can slap or grind against its guides.
- PossibleLoose blade adapter or spindleWorn spindle bearings can cause metal-on-metal grinding as the blade spins.
- PossibleDamaged deck shellA dented deck can rub against the blade or wheel during operation.
What to do
- Stop the engine immediately and disconnect the spark plug wire before investigating.
- Tip the mower and check under the deck for debris caught against the blade or deck wall.
- Spin the blade slowly by hand (plug wire disconnected) to feel for grinding, roughness, or looseness in the spindle.
- For self-propelled or riding mowers, inspect the drive belt for fraying, glazing, or misalignment.
- Check that the blade spindle isn't wobbling, which indicates worn bearings needing replacement.
- Don't run the mower again until the source of grinding is identified, since continuing can cause more damage.
Tools and parts
- Work gloves
- Wrench set
Drive beltSearch: “lawn mower drive belt replacement”
Blade spindle assemblySearch: “lawn mower spindle assembly”
When to call a pro
If the spindle bearing is worn or the belt path is damaged, a mower shop can replace the parts and check alignment.
Safety
Use caution
Always stop the engine and disconnect the spark plug wire before reaching near the blade or belt.