A lot of the rattles on my Alero were coming from the license plate itself. 3M Body Molding tape is cheap and works great to cushion the plate. Also, adjusting the black rubber feet on the trunk will help isolate any vibration of the trunk latch.
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2008 Chevrolet Silverado 1500 LT1 Z71/4x4
2000 Oldsmobile Alero GLS - Sold
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