The GMC Sierra 1500 V (GMTT1XX) Double Cab, equipped with the 5.3-liter V8 engine producing 355 horsepower and paired with an 8-speed automatic transmission, was a mainstay of GMC’s full-size pickup truck lineup from 2018 to 2021. This configuration represented a popular balance between capability, comfort, and price within the Sierra 1500 range, appealing to a broad spectrum of truck buyers. It occupied a mid-range position, offering more power and refinement than the base 2.7-liter turbocharged four-cylinder, but remaining more accessible than the top-tier 6.2-liter V8. The GMTT1XX designation refers to the truck’s platform, representing a significant update to the Sierra 1500 series.
Technical Specifications
| Brand | GMC |
| Model | Sierra 1500 |
| Generation | Sierra 1500 V (GMTT1XX) Double Cab |
| Type (Engine) | 5.3 V8 (355 Hp) 8 Automatic |
| Start of production | 2018 |
| End of production | 2021 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Pick-up |
| Seats | 5 |
| Doors | 4 |
| Fuel consumption (urban) | 13.8 l/100 km (17 US mpg, 20.5 UK mpg) |
| Fuel consumption (extra urban) | 10.2 l/100 km (23.1 US mpg, 27.7 UK mpg) |
| Fuel Type | Petrol (Gasoline) |
| Weight-to-power ratio | 6 kg/Hp, 166.5 Hp/tonne |
| Weight-to-torque ratio | 4.1 kg/Nm, 243.4 Nm/tonne |
| Power | 355 Hp @ 5600 rpm |
| Power per litre | 66.6 Hp/l |
| Torque | 519 Nm @ 4100 rpm (382.79 lb.-ft. @ 4100 rpm) |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | L84 |
| Engine displacement | 5328 cm3 (325.13 cu. in.) |
| Number of cylinders | 8 |
| Engine configuration | V-engine |
| Cylinder Bore | 96 mm (3.78 in.) |
| Piston Stroke | 92 mm (3.62 in.) |
| Compression ratio | 11:1 |
| Number of valves per cylinder | 2 |
| Fuel injection system | Direct injection |
| Engine aspiration | Naturally aspirated engine |
| Valvetrain | OHV, VVT DI |
| Engine oil capacity | 7.6 l (8.03 US qt | 6.69 UK qt) |
| Coolant capacity | 13.1 l (13.84 US qt | 11.53 UK qt) |
| Kerb Weight | 2132 kg (4700.26 lbs.) |
| Max. weight | 3130 kg (6900.47 lbs.) |
| Max load | 998 kg (2200.21 lbs.) |
| Fuel tank capacity | 91 l (24.04 US gal | 20.02 UK gal) |
| Permitted trailer load with brakes (12%) | 4309 kg (9499.72 lbs.) |
| Length | 5886 mm (231.73 in.) |
| Width including mirrors | 2063 mm (81.22 in.) |
| Height | 1921 mm (75.63 in.) |
| Wheelbase | 3745 mm (147.44 in.) |
| Drivetrain Architecture | Rear wheel drive |
| Number of gears and type of gearbox | 8 gears, 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 |
| Tires size | 255/70 R17; 265/70 R17; 265/65 R18 |
| Wheel rims size | 8.0J x 17; 8.5J x 18 |
Powertrain & Engine Architecture
The heart of this Sierra 1500 variant is the GM L84 5.3-liter V8 engine. This engine is a member of GM’s Small Block family, known for its durability and relatively simple design. The L84 utilizes direct fuel injection (DFI) and Active Fuel Management (AFM), also known as cylinder deactivation, to improve fuel economy. AFM allows the engine to shut down four cylinders during light-load driving conditions, effectively turning the V8 into a V4. The engine features an overhead valve (OHV) valvetrain with variable valve timing (VVT) on intake and exhaust valves. This combination provides a good balance of low-end torque and high-end horsepower. The 8-speed automatic transmission (8L45) is a crucial component, offering a wide gear ratio spread for both towing and fuel efficiency. It features electronically controlled shifts and is designed to handle the engine’s substantial torque output.
Driving Characteristics
The 5.3L V8 with the 8-speed automatic delivers a comfortable and capable driving experience. While not as quick as the 6.2L V8, the 355 horsepower and 382 lb-ft of torque provide ample power for everyday driving and towing. The 8-speed transmission helps keep the engine in its optimal power band, resulting in responsive acceleration. The AFM system is generally seamless, though some drivers may notice a slight vibration when transitioning between V8 and V4 modes. Compared to the manual transmission options available on other Sierra 1500 trims, the automatic prioritizes convenience and ease of use. The gear ratios are tuned for a balance of acceleration and fuel economy, making it well-suited for highway cruising and city driving.
Equipment & Trim Levels
The 5.3L V8 Double Cab was available in several trim levels, including SLE, Elevation, and SLT. Standard features typically included air conditioning, power windows and locks, a touchscreen infotainment system with Apple CarPlay and Android Auto compatibility, and a rearview camera. Higher trim levels added features such as leather upholstery, heated and ventilated front seats, a premium sound system, and advanced safety technologies like blind-spot monitoring and rear cross-traffic alert. Optional extras included a sunroof, navigation system, and various towing packages. The interior design was functional and comfortable, with a focus on durability and ease of use.
Chassis & Braking
The Sierra 1500 V (GMTT1XX) Double Cab utilizes a fully boxed frame for enhanced rigidity and strength. The front suspension features independent coil springs, while the rear suspension employs a traditional leaf spring setup. This configuration provides a good balance of ride comfort and load-carrying capacity. Brakes are ventilated discs on all four wheels, providing adequate stopping power for the truck’s weight. ABS (Anti-lock Braking System) is standard. Steering is rack-and-pinion with electric power steering, offering a responsive and comfortable steering feel. The truck’s suspension is tuned to provide a comfortable ride, even when carrying a load.
Market Reception & Comparison
The 5.3L V8/8-speed automatic combination was widely praised for its balance of power, fuel economy, and refinement. Critics noted that it offered a compelling alternative to the more expensive 6.2L V8, particularly for buyers who didn’t require maximum towing capacity. Fuel economy figures were competitive for a full-size pickup truck, with EPA estimates around 17 mpg city and 23 mpg highway. Compared to the 2.7L turbocharged four-cylinder, the 5.3L V8 offered significantly more power and towing capability, albeit at the expense of slightly lower fuel economy. The 5.3L also proved to be more reliable than some of the earlier iterations of the 2.7L turbo.
Legacy
The L84 5.3L V8 engine has a strong reputation for reliability, and the 8L45 transmission has also proven to be durable. These powertrains are generally well-regarded in the used car market. Common maintenance items include regular oil changes, spark plug replacements, and transmission fluid flushes. While AFM systems have been known to experience issues in some cases, the L84’s implementation is generally considered to be relatively reliable. As of today, well-maintained examples of the 2018-2021 GMC Sierra 1500 V Double Cab with the 5.3L V8 continue to hold their value and remain a popular choice for buyers seeking a capable and comfortable full-size pickup truck.
