The GMC Sierra 1500 III, produced from 2007 to 2010, represented a significant evolution in General Motors’ full-size pickup truck offerings. This generation, designated GMT900, aimed to blend robust capability with improved refinement and modern features. Within the Sierra 1500 lineup, the Extended Cab Long Box configuration with the 5.3-liter Vortec V8 engine and four-speed automatic transmission occupied a sweet spot, offering a balance of passenger space, cargo capacity, and towing ability. This variant was positioned as a versatile work truck and family hauler, appealing to buyers who needed more than a standard cab but didn’t require the full size of a crew cab.
Technical Specifications
| Brand | GMC |
| Model | Sierra 1500 |
| Generation | Sierra 1500 III (GMT900) Extended Cab Long Box |
| Type (Engine) | 5.3 Vortec V8 (320 Hp) Automatic FlexFuel |
| Start of production | 2007 |
| End of production | 2010 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Pick-up |
| Seats | 6 |
| Doors | 2 |
| Fuel consumption (urban) | 16.8 l/100 km (14 US mpg, 16.8 UK mpg) |
| Fuel consumption (extra urban) | 11.8 l/100 km (19.9 US mpg, 23.9 UK mpg) |
| Fuel Type | Petrol / Ethanol – E85 |
| Weight-to-power ratio | 7.4 kg/Hp |
| Weight-to-torque ratio | 5.2 kg/Nm |
| Power | 320 Hp @ 5200 rpm |
| Power per litre | 60.1 Hp/l |
| Torque | 461 Nm @ 4200 rpm (340.02 lb.-ft. @ 4200 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 | 2378 kg (5242.59 lbs.) |
| Max. weight | 3130 kg (6900.47 lbs.) |
| Max load | 752 kg (1657.88 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%) | 4309 kg (9499.72 lbs.) |
| Length | 6325 mm (249.02 in.) |
| Width including mirrors | 2029 mm (79.88 in.) |
| Height | 1870 mm (73.62 in.) |
| Wheelbase | 4001 mm (157.52 in.) |
| Front track | 1730 mm (68.11 in.) |
| Rear (Back) track | 1702 mm (67.01 in.) |
| Ride height (ground clearance) | 230 mm (9.06 in.) |
| Minimum turning circle (turning diameter) | 15.6 m (51.18 ft.) |
| Approach angle | 16.2° |
| Departure angle | 22.8° |
| Ramp-over (brakeover) angle | 18° |
| 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 variant 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 and aluminum cylinder heads, contributing to its durability. The engine utilized a traditional overhead valve (OHV) valvetrain with two valves per cylinder. Fuel delivery was handled by a multi-port fuel injection system, providing precise fuel metering for optimal performance and efficiency. The LMG engine was also FlexFuel capable, meaning it could run on gasoline or a blend of up to 85% ethanol (E85). This engine produced 320 horsepower at 5200 rpm and 340 lb-ft of torque at 4200 rpm. The engine was mated to a four-speed automatic transmission, the Hydra-Matic 4L60-E, a widely used and reliable unit. While not the most advanced transmission available at the time, it provided smooth shifts and adequate performance for most driving situations.
Driving Characteristics
The 5.3L V8 and four-speed automatic combination in the Sierra 1500 offered a comfortable and capable driving experience. Acceleration was adequate for everyday driving and towing, though not particularly sporty. The automatic transmission’s gear ratios were optimized for towing and hauling, providing sufficient low-end torque. Compared to the available 4.8L V8, the 5.3L offered a noticeable increase in power and towing capacity. However, it wasn’t as quick or fuel-efficient as the smaller engine. Compared to the 6.0L V8, the 5.3L offered a better balance of power and fuel economy, making it a more practical choice for many buyers. The ride quality was typical for a full-size pickup truck – firm but comfortable, capable of handling rough roads and heavy loads.
Equipment & Trim Levels
The Extended Cab Long Box 5.3L Sierra 1500 typically came standard with features like air conditioning, power windows and locks, a CD player, and cloth upholstery. Extended cab models added a rear seat, increasing passenger capacity. Optional extras included leather upholstery, a premium sound system, power-adjustable seats, and a navigation system. Trim levels varied, with the base model offering a more utilitarian interior, while higher trims featured more luxurious appointments. The Long Box configuration provided a substantial cargo bed, ideal for hauling large items.
Chassis & Braking
The Sierra 1500 GMT900 utilized a body-on-frame construction, providing a robust and durable platform. The front suspension featured independent coil springs, while the rear suspension employed a traditional leaf spring setup. This configuration offered a good balance of ride comfort and load-carrying capacity. Braking duties were handled by disc brakes up front and drum brakes in the rear. Anti-lock brakes (ABS) were standard, enhancing safety and control during emergency braking situations. The steering system was a rack-and-pinion setup with power assist, providing responsive and precise steering.
Market Reception & Comparison
The Sierra 1500 GMT900, and specifically the 5.3L V8/automatic combination, was well-received by critics and consumers alike. It was praised for its comfortable ride, spacious interior, and strong towing capabilities. Fuel economy was considered average for a full-size pickup truck. Compared to competitors like the Ford F-150 and Dodge Ram, the Sierra 1500 offered a competitive package with a reputation for reliability. The 5.3L engine struck a good balance between power and fuel efficiency, making it a popular choice among buyers who needed a versatile and capable truck.
Legacy
The GMT900 Sierra 1500, particularly the 5.3L V8 variant, has proven to be a durable and reliable truck. The LMG engine is known for its longevity, and with proper maintenance, can easily exceed 200,000 miles. The four-speed automatic transmission is also generally reliable, although it may require servicing at higher mileage. Today, these trucks are readily available on the used car market at affordable prices, making them a popular choice for budget-minded buyers who need a capable and dependable pickup truck. While not the most technologically advanced truck available, the Sierra 1500 GMT900 remains a solid and practical choice for work and play.
