Could be the alternator, an idler pulley bearing or the water pump, if the water pump is original, it would be suspect, you may already be riding on a replacement water pump.

Stupid simple to figure out once the belt is removed, but removing the belt is not the easiest thing to do on the 4.8l.

Make sure you have a belt routing diagram and/or take a picture or make a drawing as I recall there are different belt routings on the V8 and they differ between engine size and model.

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2008 4.8i Black with Tabacco. Black Y-spoke wheels and shadowline trim.