2025 Gmc At4 2025 Diesel Review. Gmc's heavy hauler, the sierra hd pickup with the diesel engine, is rated to tow up to 22,500 pounds conventionally or 36,000 with a gooseneck hitch fitted. Gmc is, by branding, more upscale.

Big thanks to buick gmc of brooksville for helping make this review possible! Gmc’s heavy hauler, the sierra hd pickup with the diesel engine, is rated to tow up to 22,500 pounds conventionally or 36,000 with a gooseneck hitch fitted.