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 2007 to 2010. Representing the third generation of the Sierra 1500 (GMT900 platform), this variant occupied a sweet spot for buyers needing a capable work truck with a comfortable, albeit basic, interior. It catered to individuals and businesses prioritizing utility and affordability over luxury features. 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 (320 Hp) Automatic FlexFuel |
| Start of production | 2007 |
| End of production | 2010 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Pick-up |
| Seats | 3 |
| 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 | 6.7 kg/Hp, 148.5 Hp/tonne |
| Weight-to-torque ratio | 4.7 kg/Nm, 213.9 Nm/tonne |
| 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 | 2155 kg (4750.96 lbs.) |
| Max. weight | 2903 kg (6400.02 lbs.) |
| Max load | 748 kg (1649.06 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 | 1867 mm (73.5 in.) |
| Wheelbase | 3378 mm (132.99 in.) |
| Front track | 1730 mm (68.11 in.) |
| Rear (Back) track | 1702 mm (67.01 in.) |
| Ride height (ground clearance) | 208 mm (8.19 in.) |
| Minimum turning circle (turning diameter) | 15.4 m (50.52 ft.) |
| Approach angle | 16° |
| 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 and aluminum cylinder heads. 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 adequate atomization for efficient combustion. The FlexFuel capability allowed the engine to run on gasoline, ethanol blends, or pure E85, offering drivers a choice based on price and availability. The engine produced 320 horsepower at 5200 rpm and 340 lb-ft of torque at 4200 rpm. The Hydra-Matic 4L80-E four-speed automatic transmission was the standard pairing. This transmission was known for its durability and ability to handle the engine’s torque output, but it lacked the efficiency of more modern transmissions with higher gear counts.
Driving Characteristics
The 5.3L V8 and 4L80-E automatic combination provided adequate, but not exhilarating, performance. Acceleration was sufficient for everyday driving and towing, but it wasn’t particularly quick. The four-speed automatic, while reliable, meant the engine often ran at higher RPMs during highway cruising, impacting fuel economy. Compared to the available 4.8L V8, the 5.3L offered a noticeable power increase. However, it fell short of the performance offered by the 6.0L V8 or the diesel options. The gear ratios were optimized for towing and hauling, rather than outright speed. The rear-wheel-drive configuration provided a traditional truck feel, with a focus on capability and stability when carrying a load.
Equipment & Trim Levels
The Regular Cab Long Box 5.3L Automatic Sierra 1500 typically came with a fairly basic level of equipment. Standard features included air conditioning, a basic AM/FM radio, and vinyl upholstery. Work Truck (WT) trims were even more spartan, focusing solely on functionality. Higher trims, such as SLE, added features like cloth upholstery, power windows and locks, and a better audio system. Optional extras included a CD player, cruise control, and upgraded interior trim. The interior design was functional and durable, prioritizing practicality over aesthetics.
Chassis & Braking
The GMT900 platform utilized a body-on-frame construction, providing a robust and durable chassis. The front suspension consisted of independent coil springs, while the rear suspension employed a traditional leaf spring setup. This configuration was well-suited for carrying heavy loads. Braking duties were handled by disc brakes in the front and drum brakes in the rear. Anti-lock braking system (ABS) was standard. The rear drum brakes were a cost-saving measure, and some critics noted that they didn’t offer the same stopping power as rear discs. Stabilizer bars were included to reduce body roll during cornering.
Market Reception & Comparison
The 5.3L V8 with the automatic transmission was a popular choice for Sierra 1500 buyers who needed a capable truck without the expense of the higher trims. Critics generally praised the engine’s reliability and adequate power, but noted the four-speed automatic transmission was becoming outdated. Fuel economy was average for a full-size pickup truck of that era. Compared to the 4.8L V8, the 5.3L offered a significant performance boost, making it a worthwhile upgrade for those who frequently towed or hauled heavy loads. The diesel options offered superior fuel economy and torque, but came at a higher price point.
Legacy
The LMG 5.3L Vortec V8 proved to be a remarkably durable engine. Many examples are still on the road today, often with high mileage. The 4L80-E transmission is also known for its longevity. While not the most fuel-efficient or technologically advanced powertrain, the combination of the 5.3L V8 and 4L80-E automatic offered a reliable and capable solution for truck buyers. In the used car market, these Sierra 1500s are often sought after for their affordability and work-ready capabilities. Regular maintenance, including oil changes and transmission fluid flushes, is crucial for ensuring the continued reliability of these trucks.
