DIAGNOSIS Severe vibration indicates an unbalanced load or an improperly seated container. The blender is not stable on its feet.
FIX Stop the blender. Check the container seating. It must be turned fully clockwise until locked. The handle must align with the power button. Open the lid and check the contents. For smoothies or thick mixtures, use the tamper. Never blend less than 1 liter or more than 2 liters for the 64-oz container. Start at Variable Speed 1, then slowly increase to the desired speed. Do not go directly to high speed.
IF THAT DIDN'T WORK The blender base may not be level. Check that all four rubber feet are intact and clean. Ensure the countertop surface is flat and non-slip. The vibration is often worse on granite or glass surfaces. Place the blender on a folded towel or a non-slip pad to dampen resonance.
HEADS UP The machine is loud by design. A high-pitched whine at top speed is normal. A loud, grinding, clunking vibration is not. If the problem persists with correct technique, the container drive socket may be defective.