LG LDF8764ST dishwasher squealing or grinding noise during wash cycle (spray arms spin freely)

Hi, I’m Mike—your home appliance troubleshooting expert. What kind of noise is it (grinding, buzzing, squealing, rattling) and exactly when in the cycle does it happen—during fill, spraying/washing, or draining?

Does it happen mainly while it’s spraying water (mid-cycle) or when it’s draining at the end, and is it constant through the cycle or just in the first few minutes?

Does the noise still happen on a mostly empty load, and when you spin the upper and lower spray arms by hand do they turn smoothly without wobble or scraping?

Does the squeal still occur with the dishwasher empty and both spray arms confirmed to spin freely by hand, or does it disappear?

Thanks—that points to the wash/circulation system, not the drain. On the LDF8764ST, a squeal or light grinding during the spray portion is most commonly caused by:

• Worn wash motor bearings/seal: The circulation (wash) pump runs any time it’s spraying; when its bearings wear, it makes a high‑pitched squeal or a dry, rubbing grind that gradually gets louder. Repair is usually replacing the circulation pump/motor (often sold with the sump assembly).
• Debris in the wash impeller: Small glass, seeds, or bone can lodge in the impeller volute and “sing” or grind as the pump spins. Performance may drop, and the sound can come and go.
• Pump cavitation from low water level/restricted flow: If the tub isn’t filling quite enough or the pump is starved for water, the impeller can howl/whine. Common causes are a partially clogged inlet valve screen, a sticking float, a kinked fill hose, or heavily clogged sump filters.
• Partially blocked spray‑arm jets: Even if the arms spin freely, blocked nozzles can create a high‑pitched whistle while spraying.

How to tell which is most likely:

• Constant squeal every wash and getting worse over time → circulation pump bearings.
• Noise started after a broken glass/seed incident or varies mid‑cycle → debris in impeller.
• Water coverage seems weak or level looks low, and the sound changes as it fills → low fill/cavitation.
• Cleaning performance is otherwise normal but there’s a steady, high‑pitch note → spray‑arm jet blockage.

Typical fixes and expectations:

• Circulation pump/motor replacement is the common repair; parts cost is often in the $120–$220 range plus labor.
• Debris removal involves opening the sump/pump area to clear the impeller.
• Low fill issues are addressed by cleaning/replacing the inlet valve or resolving float/filter restrictions.
• Spray‑arm issues are resolved by clearing the jet holes or replacing a damaged arm.

Safety note: If you decide to inspect anything, disconnect power and water first; there can be sharp glass in the sump. If you ever smell burning, see smoke, or the noise becomes a harsh screech, stop use and have a technician check it.

Would you like step‑by‑step checks to narrow it down (without parts) before deciding on repair?