The Sierra 2500 HD delivers a good amount of power, hauling, and towing capabilities. It comes standard with 401-hp and 464 lb-ft of torque 6.6-liter gas V8 engine. This engine provides an increase in horsepower and torque compared to the previous 6.0-liter gas engine. An optional turbocharged 6.6-liter Duramax diesel V8 with 446 hp and 910 lb.-ft. of torque, paired with a new Allison 10-speed automatic transmission is available. This new transmission provides closer gear spacing than before, allowing the engine to operate in an optimal range at all times. These changes help the GMC perform at its peak, with a maximum tow rating of up to 18,500 lbs. and a maximum Gross Combination Weight Rating of up to 27,500 lbs. Depending on your trim, Sierra HD offers a maximum payload of up to 3,979 lbs. Pricing for the Sierra HD starts at $40,000 for the Sierra SLE & SLT, $57,700 for the Sierra HD AT4, and $63,700 for the Sierra HD Denali.