GMPartsGiant.com offers the wholesale prices for genuine 2014 GMC Sierra 3500 HD Denali 2WD parts. Parts like Automatic Transmission Rear Cover are shipped directly from authorized GM dealers and backed by the manufacturer's warranty. Parts fit for the following vehicle options. Engine: 8 Cyl 6.0L Flex, 8 Cyl 6.6L Diesel. Model Code: CREW CAB 1 TON, CREW CAB 1 TON 119.0, EXTENDED CREW CAB 1 TON 161.5.