There have been reports of QDII diffs chattering due to both lack of maintenance and not using the LSD additives. Anytime you're turning the clutches need to slip against each other, however pressure is not applied to the clutch packs unless slippage is sensed. But they are still in contact with each other.
Its an easy place to start especially since the fluids supposed to be changed every 30k miles (depending on which schedule you're referring to)
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