GMC Sierra AT4 2026 Automatic Gasoline 4WD GMC AT4 Specifications __ 8 Cylinder 5.3 CC Engine Leather Seat Cooling 20-inch Rims Electric Control Seats Navigation Screen Cruise Control Electric Windows Projector 10-speed Automatic Transmission Bluetooth Keyless Start Wireless Charger Rear Camera Front and Rear Sensors Anti-slip Steering Wheel Control Electric Mirror Folding 18-inch Rim Smart Entry Smart Start Auto-dimming Mirror