2021 GMC Sierra 3500HD Review

Rear-wheel drive is standard on the Sierra, SLE and SLT trims, while four-wheel drive is optional on that trio and standard on the AT4 and Denali. A dual rear-wheel option is available on certain cab and bed configurations of the Sierra to boost the truck's towing capacity.

Sierra
The base Sierra is a relatively bare-bones truck. Standard features include:

• 18-inch steel wheels
• LED headlights and taillights
• Manually adjustable trailering mirrors
• Cargo bed steps
• Locking tailgate and spare tire carrier
• 40/20/40-split front bench seat
• Vinyl seats and floor coverings
• Manual windows and door locks (regular cab)
• Trailering hitch
• 7-inch touchscreen infotainment display
• Apple CarPlay and Android Auto smartphone integration

SLE
Adds more convenience features, such as:

• 18-inch alloy wheels
• Upgraded exterior trim
• Power trailering mirrors
• Configurable (MultiPro) tailgate
• Integrated brake trailer controller (allows adjustment of a trailer's brakes from the cab)
• Cloth seats and carpeted floors
• Front underseat storage
• Cruise control
• Power door locks and windows
• Remote keyless entry
• 4.2-inch color driver information display
• Satellite radio
• Connected services including a Wi-Fi hotspot

SLT
More luxurious than the SLE, the SLT has:

• Power-folding and extending trailering mirrors
• Cargo bed lighting
• 120-volt power outlet in cargo bed
• Keyless access with push-button engine start
• Remote engine start
• Dual-zone automatic climate control
• Leather seats
• Power-adjustable driver's seat
• Heated front seats
• Heated steering wheel
• 8-inch touchscreen infotainment system display
• Wireless functionality for Apple CarPlay and Android Auto
• High-definition backup camera with hitch-view angle

AT4
Provides more off-road attitude and capability with:

• Standard four-wheel drive
• Hill descent control
• Off-road suspension tuning
• Underbody skid plates
• Body-colored bumpers
• Spray-in bedliner
• Front bucket seats with center console
• Ventilated front seats
• Heated rear outboard seats

Denali
Tops the Sierra 3500HD lineup and adds on:

• 20-inch alloy wheels
• Automatic high-beam headlights
• Chrome exterior trim
• Power-sliding rear window
• Side steps to ease cab entry and exit
• Premium leather seats
• Upgraded driver information display
• Navigation system
• Bose premium sound system
• Wireless smartphone charging
• Bed-view camera

The Denali also includes a number of safety features and driver aids, many of which are optional on other trims.

• Forward collision mitigation (warns you of an impending collision and applies the brakes in certain scenarios)
• Lane departure warning (alerts you if the vehicle begins to drift out of its lane)
• Blind-spot monitoring with rear cross-traffic alert (warns you if a vehicle is in your blind spot during a lane change or while reversing)
• Surround-view camera system (gives you a top-down view of the Sierra 3500HD and its surroundings for tight parking situations)
• Parking sensors (alert you to obstacles that may not be visible in front of or behind the vehicle when parking)