2019 GMC Sierra launches new off-road AT4 brand 2019 GMC Sierra launches new off-road AT4 brand March 27, 2018 dzadmin Comments 0 Comment With an eye on brands such as Jeep and off-road enthusiasts, GMC will introduce AT4 variants across its lineup. Like the Denali subbrand, the AT4 lineup is expected to be priced higher than standard GMC models and generate fatter profits.