GMCW3500ForwardRear Main Seal Cover. Brand: Replacement. Fits Years: 2004, ...GMC W3500 Forward Rear Main Seal Cover. Brand: Replacement. Fits Years: 2004, 2005, 2006, 2007, 2008, 04, 05, 06, 07, 08. Engine Rear Main Seal Cover -- Engine Rear Main Seal Cover, with Gasket and Bolts - N02-114more