Summit White 2018 GMC Sierra 1500 4WD 6-Speed Automatic EcoTec3 5.3L V8 Flex Fuel 2018 GMC Sierra 1500 SLT in Summit White. Price includes: $1,000 - Chevrolet & GMC Special Package Consumer Cash. Exp. 04/30/2018, $1,000 - GM Down Payment Assistance Program. Exp. 04/30/2018, $750 - GM National Purchase Bonus Cash. Exp. 04/30/2018