The first things you will notice when starting up one of the completely redesigned 2015 Chevrolet Silverado and GMC Sierra HD pickups is what is missing: noise. At idle, the GM 2500/3500 Series trucks offer very quiet work truck interiors.
You will not mistake the sound of the diesel for a gas engine, but the diesel is very quiet, even when accelerating with a heavy (10,000-lb.) trailer in tow.
Inlaid doors fit snugly into recesses in the body for reduced turbulence, and triple door seals help reduce highway noise. Small body details, such as the roof and tailgate spoilers, were tuned in a wind tunnel to smooth airflow over the truck for reduced noise and improved aerodynamic efficiency. At speed, wind noise is pretty much nonexistent.
Our testing of the largest of GM's trucks took us to Payson, Ariz., to challenge their towing performance on some long, steep grades – one of which was about eight miles long. We pulled 10,000-lb. trailers repeatedly up and down the grades to get a good feel for how these trucks perform.
With the Duramax diesel engines and Allison transmissions, there was never a shortage of power to briskly accelerate towed loads, even uphill. The 2015 HD pickups offer three powertrains:
- Standard: 6.0L FlexFuel V8 rated 360 hp and 380 lb.-ft. of torque, matched to a six-speed automatic transmission
- Bi-fuel option: 6.0L V8 (all three cab styles) allows easy switching between gasoline and compressed natural gas
- Diesel: Duramax 6.6L turbodiesel rated 397 hp and 765 lb.-ft. of torque, mated to an Allison 1000 six-speed automatic
The Duramax features piezo-actuated fuel injectors for improved performance and efficiency, and the aforementioned variable-vane turbocharger.
The Allison 1000 transmission features 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.
A key work-truck technology GM employed on its HD models is a diesel exhaust brake that adjusts the variable vanes in the turbocharger to create additional back pressure in the engine and slow the vehicle. The exhaust brake is very quiet from the perspective of the driver’s seat; probably a function using the turbocharger vanes. Combining the exhaust brake with automatic-transmission downshifts worked flawlessly on our drives, allowing us to descend a steep, eight-mile grade with little effort and placing no additional stress on the service brakes.
GM's cruise-control interaction with the exhaust brake was impressive. Pulling a loaded trailer, we set the cruise at 55 mph at the top of the steep eight-mile grade. No other intervention was required to hold the speed at exactly 55 to the bottom of the hill.
Loads felt controlled at all times. StabiliTrak with Trailer Sway Control is now standard on all Silverado HDs, including 3500 dually models, providing additional security to the drive.
Handling felt more automotive than work truck. Light steering effort, a smooth ride that transmitted very little to the driver or passengers when encountering road patches or sections of rough road masked the vehicle's work-truck capability. Handling improved courtesy of changes in the frame and suspension.
A new family of fully boxed frames undergird the 2015 Silverado HD lineup with large cross sections, hydroforming and high-strength steels in key areas. Frame stiffness contributes to improved handling and ride comfort, while frame strength enhances payload and towing capability.
The Silverado and Sierra 2500/3500s, compared to previous models, boast:
- Maximum payload increased 2 percent to 7,374 lbs.
- Maximum conventional towing with the factory hitch is up 9 percent to 19,600 lbs.
- Maximum fifth-wheel towing is up 3 percent to 23,200 lbs.
The independent front suspension is specifically engineered for HD pickup use. Torsion bars tailored to the weight ratings of the trucks, allow easier trim height adjustment to accommodate the weight of snowplows and other accessories. Asymmetrical rear leaf springs balance ride and load capacity, and improve control of axle hop.
Drivers can easily engage and adjust the available Integrated Trailer Brake Controller at the upper left side of the dashboard. The system displays Gain on the Driver Information Center in the instrument cluster.
An upright instrument panel puts important controls within easy reach, along with a six-gauge instrument cluster with driver information center. Controls are well placed, intuitive and easy to operate even when wearing work gloves. A row of easy-to-operate switches, clearly marked, control the diesel engine exhaust brake, the tow-haul feature and cargo bed lighting.
The 2015 Silverado and Sierra HD design is based on GM's 1500 Series pickups, which were completely redesigned in 2014. Cargo box designs were carried over, bringing two-tier loading capability, integrated tie-downs, accessibility via the CornerStep rear bumper, under-rail LED lighting to illuminate cargo and available EZ Lift-and-Lower tailgate from features introduced on the Silverado and Sierra 1500. Boxes are available in 6-ft. 6-in. and 8-ft. lengths.
The Silverado/Sierra 2500/3500 HDs offer more than 150 combinations of cabs, bed lengths, powertrains and axle ratios, enabling customers to buy the right truck for a wide range of towing and hauling.