For 2015, General Motors’ heavy-duty pickups—the Chevrolet Silverado HD and the GMC Sierra HD-- feature newly sculpted exteriors designed to improve aerodynamics and cooling performance as well as redesigned interiors.

According to GM, both the Chevy and GMC models provide “segment leading” maximum payloads of 7,374 lbs and maximum conventional towing rating of up to 19,600 lbs as well as maximum fifth-wheel towing ratings of 23,200 lbs.

Diesel, gasoline and compressed natural gas (CNG) power will be available on 2500 and 3500 models in both heavy-duty pickup lines.

For the Silverado, the diesel option will continue to be the Duramax 6.6L turbodiesel mated to the Allison 1000 six-speed automatic transmission.

Rated at 397 hp and 765 lb-ft of torque, the Duramax features piezo-actuated fuel injectors for improved performance and efficiency, according to GM, and a variable vane turbocharger that also acts as an exhaust brake to help control vehicle speed when needed on long downgrades.

The Allison 1000 transmission includes a driver shift control with tap up/tap down shifting and a Tow/Haul mode that reduces shift cycling for better control and improved cooling when towing or hauling heavy loads.

The standard engine on all HD models is the 6.0L Vortec gasoline V-8, with continuously variable valve timing, matched with the Hydra-Matic 6L90 six-speed automatic transmission. The V-8 is rated at 360 hp380 lb-ft of torque on 2500 models and GM said it is specifically engineered for low-end torque. A version rated at 322 hp is standard on 3500 versions and pickups with either version are E85 FlexFuel-capable.

According to GM, a bi-fuel version of the 6.0L V-8, with special hardened valves and valve seats to enable operation on gasoline or CNG,  will be available in all HD pickups.

GM added that it will continue to work with a second-stage manufacturer to offer a single-source option for its CNG vehicles. The bi-fuel trucks are built with the specially designed engine, the fuel system is installed by GM’s Tier One supplier, and the completed vehicle is delivered directly to the customer. This process makes ordering the bi-fuel option as seamless as ordering a truck powered by gas or diesel, and ensures the highest level of durability, reliability and safety, the OEM noted.

According to Silverado executive chief engineer Jeff Luke, Silverado HD pickup updates for 2015 also include:

  • All-new exterior styling with enhanced cooling air flow, which enables Silverado’s 6.6-liter Duramax turbo diesel and 6.0-liter Vortec V-8 to better maintain full power, even under heavy loads and high ambient temperatures
  • Integrated cruise control, Auto Grade Braking and Diesel Exhaust Braking (on diesel models) that help make tough towing easier
  • Standard StabiliTrak with Trailer Sway Control on all models including 3500 duallys.
  • All new cabs and interiors that provide increased space and comfort, with extensive storage space tailored to the way customers use full-size trucks.
  • New 6.5- and 8-ft boxes with standard CornerStep bumpers, EZ Lift and Lower tailgates, and other features that make cargo handling easier.
  • Chevrolet MyLink, which provides powerful connectivity for work or family with simple, intuitive controls.

According to Tony DiSalle, vp of GMC Marketing, new and enhanced features for the 2015 Sierra HD lineup include:

  • CornerStep rear bumper, EZ Lift and Lower tailgate, standard upper tie-downs and other features that make cargo handling easier
  • Standard StabiliTrak with Trailer Sway Control on all models, including 3500HD dually
  • Integrated cruise control, auto grade braking and diesel exhaust braking (diesel models), for greater driving control and reduced brake wear on grades
  • Enhanced cooling airflow, which enables the Duramax turbo diesel and 6.0L gas engine to better maintain full power, even under heavy loads and high ambient temperatures
  • Latest-generation IntelliLink infotainment system, which offers a variety of connectivity options for devices of all types and available navigation

Both the 2015 Chevy Silverado HD and GMC Sierra HD trucks will be built at GM plants in Fort Wayne, IN, and Flint, MI.