Auto review: GMC's 2020 Sierra HD 2500 is a high-end hauler

For 2020, the GMC Sierra 2500 Denali is larger and bolder, the purpose-built exterior pairing functional design with exclusive style.

New features include a Side Bed Step in front of the rear wheel arches, power-adjustable trailer-tow mirrors, a Bed View Camera (Denali Ultimate Package, $2,870), camera-based Adaptive Cruise Control andHD Surround Vision (Ultimate Package).

My ruggedly handsome Sierra 2500 Denali was Carbon Black Metallic ($495) with signature multidimensional Denali grille featuring high-gloss mesh and chrome inserts, chrome vertical front recovery hooks, chrome six-inch assist steps and distinct 20-inch multidimensional polished aluminum wheels with all-terrain tires.

High-intensity LED headlights, signature C-shaped LED light-blade daytime running lights, LED taillights and fog lights are standard.

Power was provided by a 445-horsepower 6.6-liter Duramax Turbo-Diesel V-8 engine ($9,750), connected to an Allison 10-speed automatic transmission, producing up to 910 foot-pounds of torque. Air drawn through the hood scoop and the large front grille by the dual-path Diesel Intake System provided cooler induction air to maximize horsepower and optimize trailering performance.

An exhaust brake restricted exhaust to create back pressure, retarding engine speed to offer supplemental braking — so effectively that it can slow a heavy vehicle on a downgrade without the use of mechanical brakes.

Tow/Haul mode offers better control and improved cooling when towing or hauling heavy loads and comes with a reminder to engage when a trailer is detected.

Auto Grade Braking (active in Tow/Haul mode) automatically downshifts to enable engine braking on downhill grades, reducing brake wear.

Useful during my review week, engine block heating eased cold-weather starts. Engine After Run keeps the engine running for up to 15 minutes to allow cooling after a strenuous haul, using the fan and coolant.

An automatic-locking rear differential is standard and reacts in milliseconds in low traction to improve safety on slippery surfaces.

As a heavy-duty work truck, Sierra Denali has an innovative, expanded Prograde Trailering System to improve connecting and driving with a trailer. Features are accessible through the infotainment system and include: Trailer Light Test for one-person checking of brake lights, turn signals, etc; Customizable Trailer Profiles to save information such as trailer mileage, maintenance intervals, brake level settings, etc; Trailer Tire Pressure and Temperature Monitoring using a set of RF wireless sensors installed on the trailer wheels to send info to the app screen; customizable Pre-Departure Checklists on the screen with clear, illustrated examples of required steps; and Trailer Theft Alert to flash exterior lights and sound the horn if the trailer is disconnected while the vehicle is parked and locked.

The package also includes dynamic Hitch Guidance with Hitch View camera zoom. Many features of the trailering system can also be accessed and initiated through the My GMC mobile app, including the ability to share trailers and trailer profiles with other drivers.

ProGrade Trailering also includes auto electric parking brake assist, trailer sway control and trailer brake controller.

The interior was stylish and luxurious, with Denali-exclusive premium Forge Dark Walnut/Dark Ash leather seating, open-pore ash wood armrest and console trim and subtle dark-finish aluminum décor. Heated and ventilated front seats, heated steering wheel and heated outboard rear seats are standard.

A Bose seven-speaker audio system, Wi-Fi, Apple Car Play and Android Auto, SiriusXM, OnStar services and GMC Connected Access are standard. Teen Driver is standard, allowing parents to set controls and review teen driving habits.

The Back Seat Reminder is standard along with forward collision alert, lane-keep assist with lane-departure warning, automatic emergency braking, Intelli Beam headlights and adaptive cruise control with following-distance indicator. Front and rear park assist, lane-change alert with side blind-zone alert and rear cross-traffic alert safety systems are also standard.