As I backed the beast of a pickup into the lumber yard, the forklift operator took a long look and shouted, "Nice truck!" I thanked him and hauled away 1,500 lb of river rock, leaving space for many hundreds more before reaching the full cargo rating of the 2015 GMC Sierra Denali HD 2500 pickup.

General Motors, which lent ENR a rig to test out for one week in May, has refreshed its heavy-duty pickups with the latest Chevrolet Silverado and GMC Sierra light-truck features, including bolder looks, sumptuous interiors and handy hauling tools. The Sierra Denali HD—which stands for heavy duty—is the top trim in the lineup, carrying a starting price of $50,540. The truck I tested stickered for $63,835 including delivery fees.

New to the HD trucks are useful apps and safety technologies that include lane departure warning and collision avoidance. During a routine drive, I discovered that this boss of pickups is also a bit of a bossypants: Approach another vehicle too quickly, and the truck startles you with red alerts flashed onto the windshield, more lights on the dashboard and sharp buzzes to your fanny. The only thing missing was a lecture from Sister Catherine over the audio system. Additionally, a backup camera and parking sensors proved invaluable for maneuvering the Denali HD, which only comes in a longer crew-cab model.

The GMC also came equipped with an 8-in. Intellilink touchscreen, which displays helpful apps, though they are slow to boot up. It usually responded well to voice commands, and climate control can also be manipulated digitally, though I found it easier to use the old-fashioned knobs. The rest of the center console was packed with nooks and crannies, including a 110-volt receptacle, a rubber tray to prop up smartphones and a two-tiered storage bin under the armrest. Rear seats flip up with one hand, which is helpful for storing bulky objects in the cab, though the floor is not completely flat.

ENR's luxury Denali model came trimmed out in soft, supportive leather seats with contrast stitching—including a heated steering wheel and heated-and-cooled seats. Even so, all the new HD pickups are capable work vehicles. Available in three-quarter and one-ton sizes, the trucks come standard with a 6.0-liter V-8 that cranks out 360 horsepower and 380 lb-ft of torque.

Our three-quarter-ton test truck was equipped with an optional 6.6-liter Duramax turbodiesel V-8, which offers 397 hp and a whiplash-inducing 765 lb-ft of twist. Equipped with a conventional hitch, the HD trucks can tow up to 19,600 lb and carry up to 7,374 lb in the bed. Towing soars to 23,200 lb with dual rear wheels and a fifth-wheel hitch. Our test truck rolled with a six-speed Allison automatic transmission, which shifted up seamlessly and downshifted in good time, saving brake wear. Like the Allison, an engine exhaust brake comes with the diesel.

Traditionalists will be glad to know that the truck still uses conventional power steering and a column-mounted shifter, but some analog gauges have gone digital, a move that saves weight and hardware. Still, I wish GM had carved out space for a gauge showing diesel exhaust fluid (DEF), especially as my test truck suddenly ran out, warning me that my speed would soon be limited. I rushed to an auto parts store for a jug costing $7.48, though truck stops carry DEF for less than $3 per gal. GM estimates that the 5-gal DEF tank consumes 1 gal per 1,000 miles.

Outside, the trucks' new rear-bumper step is a helpful addition for climbing into the bed. Also standard on most models are a torsion-bar-assisted locking tailgate, LED bed light, cargo cleats, electronic stability control and trailer sway control. Potholes were no match for our truck's off-road package, and my river rock hardly punished the bed's thick spray-on bed liner. As for fuel economy, I observed 13.8 mpg mainly in city driving for a truck that weighs more than 3.5 tons.