Had the Buick dealer perform a flush on the rear diff with a speical lubricant to refill and it worked for awile. There only recommdation was to replace the rear, which is cost prohibitve. This noise is a whing/moaning noise when turning sharp, like into driveways, streets and parking places, only when the weather and vehicle are warm. Doesnt’ seem to effect any operation, the noise has not gotton louder. Any fixes known? I may start looking for a used rear asm, but I don’t want to get the same problem, as Ive heard this is common for GMs AWD systems.