For sale: GMC Sierra AT4, 2021 model, crew cab, 5.3 V8, GCC specs, very clean. The engine, thank God, is very clean, personally used and well cared for. Anyone looking for a clean Sierra AT4 crew cab knows the value of these specifications. Specifications: AT4, crew cab, 5.3 V8, 4WD 4x4, GCC. Mileage: 136,283 km. Interior is very clean. Engine: personal use. Abu Dhabi. Note, with full transparency: two panels have been repainted due to a minor accident.