What might cause Porsche Cayenne front differential noise?

The most obvious reason You're going to hear noise from the front differentials on the Porsche Cayenne is going to be because of worn bearings or a low level of oil. It's easy to address the latter; You can use standard SAE lubricant here. Replacing the bearings is obviously going to be a bit more expensive; and there's another consideration: Sometimes You can get noise that sounds like it's the differential, when it's really the tires, if they've worn unevenly. Check these first, before You shell out money for some expensive repairs that You don't actually need!