2025 Gmc Sierra Hd At4x. 2025 sierra hd at4x & at4x aev edition the first ever sierra hd at4x and at4x aev edition is taking the at4 experience to the next level. For the 2025 model year, gmc has increased the sierra hd's maximum towing capability, but in a surprising place.
There’s more, of course, with the 2025 gmc sierra hd at4x. With the sierra hd, it adds to the at4x model by swapping on stamped steel bumpers with integrated recovery hooks and a place for a front winch.