The GMC Sierra 1500 III, specifically the Regular Cab Long Box configuration with the 5.3-liter Vortec V8 engine and automatic transmission, was a mainstay of GMC’s full-size pickup truck lineup from 2010 to 2013. Representing the GMT900 generation, this variant occupied a sweet spot for buyers needing a capable work truck without the added cost and complexity of higher trim levels or extended cab configurations. It was positioned as a robust, reliable, and affordable option within the broader Sierra 1500 range, appealing to both commercial users and individual truck enthusiasts. The FlexFuel capability added versatility, allowing operation on gasoline or ethanol blends up to E85.
Technical Specifications
| Brand | GMC |
| Model | Sierra 1500 |
| Generation | Sierra 1500 III (GMT900) Regular Cab Long Box |
| Type (Engine) | 5.3 Vortec V8 (315/326 Hp) Automatic FlexFuel |
| Start of production | 2010 |
| End of production | 2013 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Pick-up |
| Seats | 3 |
| Doors | 2 |
| Fuel consumption (urban) | 15.7 l/100 km (15 US mpg, 18 UK mpg) |
| Fuel consumption (extra urban) | 11.2 l/100 km (21 US mpg, 25.2 UK mpg) |
| Fuel Type | Petrol / Ethanol – E85 |
| Weight-to-power ratio | 6.9 kg/Hp, 145.8 Hp/tonne |
| Weight-to-torque ratio | 4.8 kg/Nm, 210.1 Nm/tonne |
| Power | 315 Hp @ 5200 rpm |
| Power per litre | 59.1 Hp/l |
| Power (Ethanol – E85) | 326 Hp @ 5300 rpm |
| Power per litre (Ethanol – E85) | 61.2 Hp/l |
| Torque | 454 Nm @ 4400 rpm (334.85 lb.-ft. @ 4400 rpm) |
| Torque (Ethanol – E85) | 472 Nm @ 4400 rpm |
| Maximum engine speed | 6000 rpm |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | LMG |
| Engine displacement | 5328 cm3 (325.13 cu. in.) |
| Number of cylinders | 8 |
| Engine configuration | V-engine |
| Cylinder Bore | 96.01 mm (3.78 in.) |
| Piston Stroke | 91.95 mm (3.62 in.) |
| Compression ratio | 9.9:1 |
| Number of valves per cylinder | 2 |
| Fuel injection system | Multi-port manifold injection |
| Engine aspiration | Naturally aspirated engine |
| Valvetrain | OHV |
| Engine oil capacity | 5.7 l (6.02 US qt | 5.02 UK qt) |
| Coolant capacity | 14.1 l (14.9 US qt | 12.41 UK qt) |
| Kerb Weight | 2161 kg (4764.19 lbs.) |
| Max. weight | 2903 kg (6400.02 lbs.) |
| Max load | 742 kg (1635.83 lbs.) |
| Trunk (boot) space – maximum | 2138 l (75.5 cu. ft.) |
| Fuel tank capacity | 128 l (33.81 US gal | 28.16 UK gal) |
| Permitted trailer load with brakes (12%) | 4536 kg (10000.17 lbs.) |
| Length | 5702 mm (224.49 in.) |
| Width including mirrors | 2031 mm (79.96 in.) |
| Height | 1872 mm (73.7 in.) |
| Wheelbase | 3378 mm (132.99 in.) |
| Front track | 1732 mm (68.19 in.) |
| Rear (Back) track | 1702 mm (67.01 in.) |
| Ride height (ground clearance) | 228 mm (8.98 in.) |
| Minimum turning circle (turning diameter) | 15.4 m (50.52 ft.) |
| Approach angle | 15.4° |
| Departure angle | 24.1° |
| Ramp-over (brakeover) angle | 21.5° |
| Drivetrain Architecture | Rear wheel drive |
| Drive wheel | Rear wheel drive |
| Number of gears and type of gearbox | 6 gears, automatic transmission Hydra-Matic |
| Front suspension | Independent coil spring |
| Rear suspension | Rigid axle suspension, Leaf spring |
| Front brakes | Disc, 330×30 mm |
| Rear brakes | Drum, 295×60 mm |
| Assisting systems | ABS (Anti-lock braking system) |
| Steering type | Steering rack and pinion |
| Power steering | Electric Steering |
| Tires size | 245/70 R17 |
| Wheel rims size | 7.5J x 17 |
Powertrain & Engine Architecture
The heart of this Sierra 1500 was the 5.3-liter (325 cubic inch) Vortec 5300 V8 engine, designated the LMG code. This engine was a member of the Vortec family, known for its robust construction and relatively simple design. It featured a cast iron block with aluminum cylinder heads, and utilized a traditional overhead valve (OHV) valvetrain with two valves per cylinder. Fuel delivery was handled by a multi-port fuel injection system, providing adequate atomization for efficient combustion. The LMG engine benefitted from Active Fuel Management (AFM), also known as cylinder deactivation, which shut down four cylinders during light-load cruising to improve fuel economy. The Hydra-Matic 6L80E six-speed automatic transmission was the sole transmission offering for this configuration. This transmission was known for its smooth shifting and durability, and its six forward gears helped to optimize engine efficiency and provide acceptable acceleration.
Driving Characteristics
The 5.3L V8 with the 6L80E automatic provided a balance between power and fuel economy. While not a performance-oriented setup, it delivered sufficient torque for everyday driving and hauling. Acceleration was adequate, but not brisk, with a 0-60 mph time estimated around 7.5-8.5 seconds. The automatic transmission’s gear ratios were tuned for towing and hauling, resulting in a relatively conservative shift pattern. Compared to the available 6.2L V8, this variant offered less outright power, but it was significantly more fuel-efficient. Against the 4.8L V8, the 5.3L provided a noticeable increase in both horsepower and torque, making it a more versatile choice for those who frequently towed or carried heavy loads. The FlexFuel capability allowed for the use of E85, which slightly increased horsepower but reduced fuel economy.
Equipment & Trim Levels
The Regular Cab Long Box 5.3L Automatic Sierra 1500 typically came standard with features like air conditioning, power windows and locks, a basic audio system, and vinyl upholstery. Work Truck (WT) trims were very basic, focusing on functionality. SLE trims added features like cloth upholstery, upgraded audio systems, and keyless entry. Optional extras included a navigation system, leather upholstery, a premium audio system, and various towing packages. The interior was functional and durable, prioritizing practicality over luxury.
Chassis & Braking
The GMT900 Sierra 1500 utilized a body-on-frame construction, providing a robust and durable platform. The front suspension consisted of independent coil springs, while the rear suspension employed a traditional leaf spring setup. This configuration was well-suited for handling heavy loads. Brakes were disc brakes in the front and drum brakes in the rear. ABS (Anti-lock Braking System) was standard. The rear drum brakes were a cost-saving measure, and while adequate for most applications, they didn’t offer the same stopping power as four-wheel disc brakes.
Market Reception & Comparison
The 5.3L V8/automatic combination was a popular choice for Sierra 1500 buyers. Critics praised its reliability and versatility, but noted that it wasn’t the most exciting powertrain option. Fuel economy was considered average for a full-size pickup truck. Compared to the 4.8L V8, the 5.3L offered a significant performance upgrade without a substantial penalty in fuel economy. The 6.2L V8 provided more power, but at a higher price point and with lower fuel efficiency. The FlexFuel capability was seen as a positive feature, offering drivers the option to utilize renewable fuel sources.
Legacy
The LMG 5.3L Vortec V8 and 6L80E transmission pairing proved to be a durable and reliable combination. These engines are known for their longevity, and well-maintained examples can still provide years of service. In the used car market, this Sierra 1500 variant remains a popular choice for buyers seeking a capable and affordable work truck. While not the most technologically advanced pickup truck, its simplicity and robustness have contributed to its enduring appeal. Common issues include oil leaks and occasional AFM solenoid failures, but these are generally relatively inexpensive to repair.
