How were you able to inspect the inner rings? The unremovable rollers preclude a good inspection. I've seen spalls as small as 2mm cause a good hum. This plus the fact that this bearing is an outer rotating design puts a lot of stress on the loaded side of the inner ring when compared with the outer ring. Did you see any soft dents on any of the races?

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95 E320 Cabriolet, 169K