He also needs to check the center carrier bearing, the rubber mount can be getting weak.

Before getting all bent out of shape, the Haldex system should have the oil drained and filter cleaned/replaced. Since there are no error messages, the Haldex computer board should still be in good shape.

There is a differential, has the diff oil level been checked? Most of us have never changed that oil and not had problems.
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My back feels better when I sit in a Volvo seat