GMC ≫ SierraGMC Sierra 2500 HD AT4 (2020, fourth generation) photosby Joshua ThompsonThe 2020 GMC Sierra 2500 HD AT4 has offroad suspension with Rancho shocks, Eaton locking rear differential, skid plates, and offroad traction control mode. ◄ PrevNext ►Credit: GMC 2020 GMC Sierra HD AT4 Interior Tags:2500at4fourth generationgmchdsierra