washer makes a super loud grinding or thumping noise only on the spin cycle, it's shaking the whole floor.

Diagnosis

The violent shaking and grinding noise during the spin cycle of the LG WM4000HWA are typically caused by a failure in the machine's ability to maintain centrifugal equilibrium. When the drum reaches high RPMs (up to 1,200 RPM on this model), any offset in weight creates a massive amount of kinetic energy. If the load is "clumped" or if you are washing a single heavy item like a bath mat or a heavy duvet, the internal sensors detect the imbalance. While the machine attempts to correct this by rotating the drum slowly to redistribute the clothes, a failure to do so triggers the "uE" or "UE" (Unbalanced Error) code, leading to the thumping you feel through the floor.

However, if the noise is a metallic grinding rather than just a thumping, the issue is likely mechanical. The LG TurboWash series uses a "spider arm" (the three-pronged support bracket) that holds the drum. Over time, detergent buildup and minerals cause galvanic corrosion, eating away at the aluminum arms. When the spider arm cracks or fails, the drum loses its center of gravity and physically strikes the outer tub during high-speed spins. You can confirm this by manually spinning the drum with your hand while the machine is off; if you feel a "click" or see the drum wobble vertically relative to the outer tub, the spider arm is compromised.

How to Fix It

If the issue is load-related, follow these steps to stabilize the machine and clear the error:

1. Press the Start/Pause button to stop the cycle immediately.
2. Open the door and manually rotate the drum to find where the clothes have clumped.
3. Unbundle any twisted sheets or towels. If you are washing a single heavy item, add 2-3 smaller towels of similar fabric to create a counter-balance.
4. Ensure the washer is perfectly level. Place a bubble level on top of the machine. If it is tilted, rotate the locking nuts on the four leveling legs clockwise or counter-clockwise until the bubble is centered.
5. Tighten the lock nuts firmly against the base of the machine to prevent the legs from vibrating loose over time.
6. Close the door and select the Spin Only cycle to test the stability before resuming a full wash.

If That Didn't Work

• Inspect and Replace Shock Absorbers: The WM4000HWA relies on two friction dampers at the bottom of the tub. If the grease inside these dampers leaks or the springs weaken, the tub will bounce uncontrollably. Access the bottom panel and check for oil leaks around the dampers. Replace both dampers simultaneously to ensure equal tension.
• Verify Shipping Bolt Removal: If the machine was recently moved or installed, ensure the four shipping bolts (located on the rear panel) were completely removed. If even one bolt remains, the suspension cannot move, and the machine will attempt to "walk" across the room during the spin cycle.
• Check the Rear Drum Bearing: A loud, high-pitched grinding sound often indicates the rear tub bearing has failed. With the drum empty, push the top of the inner drum toward the back of the machine. If there is more than 2-3mm of play (movement), the bearing has worn out and the entire outer tub assembly must be replaced.
• Clean the Drain Pump Filter: A partial clog in the pump filter (located behind the small door at the bottom left) can prevent the machine from draining fully before the spin cycle. Water remaining in the drum adds significant weight and causes an imbalance. Unscrew the filter, clear out lint and coins, and reinstall.

Heads Up

• Avoid Over-Sudsing: Excessive use of non-HE detergent creates a "cushion" of foam that can trick the balance sensors and accelerate the corrosion of the spider arm.
• Load Variety: Never wash a single heavy item (like a single bath rug) alone. Always pair heavy items with other heavy items to maintain a symmetrical load.
• Leveling Maintenance: Check the leveling legs every six months. The high-speed vibration of the TurboWash 360 can gradually loosen the lock nuts, causing the machine to tilt.
• Load Capacity: Do not pack the drum to the brim. Leave about a hand-width of space at the top to allow clothes to move and redistribute during the spin transition.