The GMC Sierra 1500 V (GMTT1XX) Crew Cab Standard Box AT4 3.0 Duramax TD, produced from 2019 to 2021, represents a significant offering in the increasingly popular full-size pickup truck segment. This variant, equipped with a 3.0-liter Duramax turbocharged diesel engine producing 277 horsepower and 459.5 lb.-ft. of torque, paired with a 10-speed automatic transmission and four-wheel drive, aimed to bridge the gap between gasoline-powered options and the heavier-duty diesel trucks in GMC’s lineup. It occupied a mid-to-upper trim level within the Sierra 1500 range, focusing on capability, refinement, and a blend of on-road comfort and off-road prowess. The AT4 trim specifically targeted buyers seeking a more adventurous lifestyle without sacrificing everyday usability.
Technical Specifications
| Brand | GMC |
| Model | Sierra 1500 |
| Generation | Sierra 1500 V (GMTT1XX) Crew Cab Standard Box |
| Type (Engine) | AT4 3.0 Duramax TD (277 Hp) 4WD Automatic |
| Start of production | 2019 |
| End of production | 2021 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Pick-up |
| Seats | 5 |
| Doors | 4 |
| Fuel consumption (urban) | 10.7 l/100 km (22 US mpg) |
| Fuel consumption (extra urban) | 9 l/100 km (26.1 US mpg) |
| Fuel Type | Diesel |
| Weight-to-power ratio | 8.7 kg/Hp |
| Weight-to-torque ratio | 3.9 kg/Nm |
| Power | 277 Hp @ 3750 rpm |
| Torque | 623 Nm @ 1500 rpm (459.5 lb.-ft. @ 1500 rpm) |
| Maximum engine speed | 5100 rpm |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | LM2 |
| Engine displacement | 3000 cm3 (183.07 cu. in.) |
| Number of cylinders | 6 |
| Engine configuration | Inline |
| Cylinder Bore | 84 mm (3.31 in.) |
| Piston Stroke | 90 mm (3.54 in.) |
| Compression ratio | 15:1 |
| Number of valves per cylinder | 4 |
| Fuel injection system | Diesel Commonrail |
| Engine aspiration | Turbocharger, Intercooler |
| Valvetrain | DOHC |
| Engine oil capacity | 6.6 l (6.97 US qt | 5.81 UK qt) |
| Coolant capacity | 20.7 l (21.87 US qt | 18.21 UK qt) |
| Kerb Weight | 2422 kg (5339.6 lbs.) |
| Max. weight | 3221 kg (7101.09 lbs.) |
| Max load | 799 kg (1761.49 lbs.) |
| Fuel tank capacity | 83 l (21.93 US gal | 18.26 UK gal) |
| AdBlue tank capacity | 20.3 l (5.36 US gal | 4.47 UK gal) |
| Permitted trailer load with brakes (12%) | 4037 kg (8900.06 lbs.) |
| Length | 6128 mm (241.26 in.) |
| Width including mirrors | 2063 mm (81.22 in.) |
| Height | 1987 mm (78.23 in.) |
| Wheelbase | 3989 mm (157.05 in.) |
| Drivetrain Architecture | All wheel drive (4×4). ICE drives rear wheels, front wheels engaged via clutch. |
| Number of gears | 10 |
| Gearbox type | Automatic transmission |
| Front suspension | Independent coil spring |
| Rear suspension | Rigid axle suspension, Leaf spring |
| Front brakes | Ventilated discs, 330×30 mm |
| Rear brakes | Ventilated discs, 345×20 mm |
| Tire size | 255/70 R17; 265/70 R17 |
| Wheel rims size | 8J x 17 |
Powertrain & Engine Architecture
The heart of this Sierra 1500 AT4 is the GM LM2 3.0-liter inline-six cylinder Duramax diesel engine. This engine represents a departure from traditional V8 diesel offerings, prioritizing efficiency and refinement. The LM2 utilizes a common-rail direct injection system, delivering fuel at extremely high pressures for optimized combustion. A variable geometry turbocharger (VGT) with an intercooler further enhances performance and reduces turbo lag. The engine also incorporates a diesel particulate filter (DPF) to meet stringent emissions standards. The 10-speed automatic transmission, co-developed with Ford, provides a wide gear ratio spread, optimizing both fuel economy and towing capability. This transmission allows the engine to operate within its optimal power band more frequently, contributing to responsive acceleration and smooth shifting.
Driving Characteristics
The 277 horsepower and 459.5 lb.-ft. of torque delivered by the LM2 Duramax, combined with the 10-speed automatic, provides a compelling driving experience. While not as overtly powerful as some of the gasoline-powered V8 options, the diesel offers a broad, flat torque curve, making it exceptionally capable for towing and hauling. The 10-speed transmission keeps the engine in its sweet spot, providing ample power for merging and passing. Compared to the 5.3L or 6.2L V8s, the Duramax offers superior fuel economy, particularly during highway driving. The AT4 trim’s suspension tuning provides a comfortable ride on paved roads while maintaining respectable off-road capability. The four-wheel-drive system offers various modes for different terrains, enhancing traction and control.
Equipment & Trim Levels
The AT4 trim level came standard with a host of features designed to appeal to active lifestyle buyers. These included a leather-appointed interior, heated and ventilated front seats, an 8-inch touchscreen infotainment system with Apple CarPlay and Android Auto compatibility, a Bose premium sound system, and a suite of advanced safety features such as automatic emergency braking, lane departure warning, and forward collision alert. Optional extras included a power-adjustable steering column, a panoramic sunroof, and a trailering package. The exterior styling of the AT4 featured unique grille and wheel designs, along with blacked-out accents, giving it a more rugged appearance.
Chassis & Braking
The Sierra 1500 AT4 utilizes a fully boxed frame for enhanced rigidity and durability. The front suspension consists of independent coil springs, while the rear suspension employs a traditional leaf spring setup. This configuration balances ride comfort with load-carrying capacity. The braking system features ventilated discs at all four corners, providing ample stopping power. ABS (Anti-lock Braking System) is standard. The AT4 trim typically included a higher-capacity rear axle and a more robust suspension system compared to lower trim levels, further enhancing its towing and off-road capabilities.
Market Reception & Comparison
The GMC Sierra 1500 Duramax diesel received generally positive reviews from automotive critics. It was praised for its fuel efficiency, smooth ride, and strong towing capability. However, some reviewers noted that the engine’s power output was not as impressive as some of its competitors, particularly the larger V8 diesels offered by Ford and Ram. Compared to the gasoline-powered Sierra 1500 trims, the Duramax offered significantly better fuel economy, but came at a higher initial cost. The AT4 trim level was well-received for its blend of luxury, capability, and distinctive styling.
Legacy
The LM2 Duramax engine has proven to be a relatively reliable powertrain, with few widespread issues reported. The 10-speed automatic transmission has also demonstrated good durability. On the used car market, the 2019-2021 Sierra 1500 AT4 3.0 Duramax TD holds its value well, appealing to buyers seeking a fuel-efficient and capable full-size pickup truck. Regular maintenance, including timely oil changes and DPF servicing, is crucial for ensuring the long-term reliability of this powertrain. The introduction of this engine marked a shift towards smaller, more efficient diesel options in the full-size truck segment, paving the way for future advancements in diesel technology.
