2020 GMC Sierra HD Denali and AT4 first drive: Polished workhorses

Recently, GMC applied the formula for these two swanky trim levels to their latest, most expensive and most capable truck—the freshly-minted GMC Sierra HD.
The Sierra HD just received the same thorough redesign as its Silverado HD cousins for 2020. The trucks sit on a new chassis, riding on longer wheelbases (over 5-inches on Crew Cabs), with beefier construction and components throughout. The stronger frame allowed GM to boost its maximum tow capacity to a whopping 35,500 pounds on single-cab dual rear-wheel models—52 percent greater than the outgoing truck.
GMC (and Chevrolet) are still the outliers when it comes to 4WD heavy-duty pickups. Ford and Ram use solid axles at each end of the chassis. But the new GM trucks ride on an improved version of the independent torsion bar front suspension and conventional leaf spring solid axle rear. The benefits, GMC says, includes improved ride, steering and even off-road capability (which is debatable). More importantly to many heavy-duty truck owners is that the torsion bar suspension is adjustable. So, when it comes time to hitch up the snow plow, GMC drivers can crank up the front end to level the chassis.