From its inception 55 years ago, the small-block V-8 has been a dependable workhorse for millions of truck customers. That heritage continues with the new 2011 Chevy Silverado heavy-duty trucks, which come standard with the Vortec 6.0L V-8 that is revised for improved performance.
A new camshaft profile for the 6.0L (engine code L96) engine helps it deliver more torque at lower rpm, for greater launch performance – particularly at higher altitudes and when towing. It also enhances idle smoothness.
The 6.0L is backed by a state-of-the-art 6L90 six-speed automatic transmission – itself a legacy of GM’s Hydra-Matic heritage, which in 1940 introduced the basic automatic transmission design used by most vehicles today. Paired in the new heavy-duty trucks, the Vortec 6.0L and 6L90 combine to deliver exceptional horsepower and torque for hauling and towing.
In fact, the 2011 heavy-duty trucks weigh more than their predecessors, but engineers optimized the performance of the Vortec 6.0L and 6L90 transmission to provide comparable fuel economy – and perhaps slightly improved efficiency (testing is ongoing) – with greater capability. The maximum towing capacity with a 6.0L/6L90 combination increases to 14,700 pounds (6,668 kg) with a fifth-wheel hitch – a 13-percent increase over previous models. It’s also nearly 30 percent more than the 11,350-pound (5,148 kg) maximum rating for the Ram heavy-duty with the 5.7L gas engine and five-speed automatic.
“Technologies such as variable valve timing in the 6.0L and double overdrive gears in the 6L90 make this a leading combination for power, efficiency and drivability,” said Jordan Lee, assistant chief engineer for V-8 engines. “The classic small-block architecture helps builds power quickly at low rpm, where it counts the most in a truck – peak horsepower is reached by only 5,400 rpm, while peak torque occurs at only 4,400 rpm.”
Indeed, the torque curve of the 6.0L is broad and flat, with approximately 90 percent of peak torque available at only 2,000 rpm. The engine’s excellent, wide-ranging performance is due in no small part to high-flow aluminum cylinder heads – a staple of the Gen III/Gen IV Vortec engines – that are based on the design of high-performance heads that first made their appearance on Corvette engines. With the new camshaft, those performance characteristics are enhanced.
Correspondingly, the 6L90 six-speed is enhanced for greater strength, smoothness and quietness. That was accomplished by:
- Adding four attachment bosses to the transfer case adapter (4WD models) for increased strength and smoother, quieter performance
- Increasing the cross section size of the transfer case adapter for greater strength
- Adding a new, stronger output shaft
- Adding a new heat shield and vent hose
“Constant power is carried across each transmission shift, for greater performance and improved drivability,” said Scott Kline, assistant chief engineer for truck transmissions. “Just as important, the feeling of performance is enhanced, too, giving the driver a greater feeling of control and confidence.”
Vortec 6.0L details
The Vortec 6.0L features a cast-iron cylinder block, aluminum heads and variable valve timing. It was developed for heavy-duty applications and has undergone the most rigorous lab- and road-testing process in small-block history. It is validated to achieve 200,000 miles of operation in typical applications.
An industry-exclusive cam-in-block variable valve timing (VVT) system allows the engine to take advantage of late intake valve closing for greater efficiency. VVT eliminates the compromise inherent in conventional fixed valve timing and allows a previously unattainable mix of low-rpm torque – even torque delivery over a broad range of engine speeds – and free-breathing, high-rpm horsepower.
The 6.0L is from GM’s family of Gen IV engines, which are based on the Gen III family that introduced host of advanced technologies to the overhead-valve V-8 – including aluminum cylinder heads, a thermoplastic intake manifold and electronic throttle control. Additional details include:
- Cylinder heads designed with replicated ports that are identical in every detail, allowing constant cylinder-to-cylinder airflow
- Coil-near-plug ignition features an individual coil for each spark plug to deliver maximum voltage and consistent spark density, with no variation between cylinders
- The valvetrain was developed with lightweight components for efficiency and performance
- A steel camshaft provides excellent durability
- Steel roller rockers add stiffness, allowing greater engine speed with less vibration
- Hydraulic roller lifters reduce friction for better fuel economy and wear resistance
Importantly, an iron cylinder block provides the foundation for the 6.0L engine used in the Silverado HD trucks. It is a robust design that has garnered great respect with truck customers for its strength and durability. The block has a long-skirt design, with the crank case extended below the crankshaft centerline. This design bolsters strength and enables cross-bolted main bearing caps – a feature that also enhances strength, while also providing more accurate location of the crankshaft and main caps.
Gen IV engines share low-maintenance features, such as anticipated spark plug life of 100,000 miles and engine coolant that maintains its cooling and corrosion-inhibiting properties for 150,000 miles. Scheduled maintenance is limited to oil changes, and thanks to GM’s industry-leading Oil Life System, a customer should never pay for an unnecessary change. The Vortec 6.0L’s ECM records engine temperature, length of operation at a given temperature and several other operating parameters, and then indicates an oil change when it’s actually needed, rather than according to a predetermined interval.
Inside the 6L90 six-speed
The 6L90 is the strongest of GM’s family of Hydra-Matic six-speed automatic transmissions. Designed for heavy-duty truck applications, it is based on the 6L80 six-speed automatic, with a strengthened input gear set – which has two additional pinion gears, for six total – and a strengthened output gear set, which uses wider gears.
Flexibility in the basic design of the transmission enabled engineers to enhance the strength of the 6L80 to suit requirements of the Chevy Silverado and GMC Sierra heavy-duty trucks, including an additional clutch plate for greater clamping strength. The 6L90 shares about 75 percent of its parts with the 6L80 and the case is slightly longer.
The 6L90 offers drivers shift control, with tap up/tap down shifting, and grade braking. Its wide overall ratio spread of 6.04:1 allows a “steep” first gear, as well as very “tall” overdrive top gear for low-rpm highway cruising. With this wide ratio spread, acceleration is maximized, as is fuel economy. Engine noise is also lower during cruising. Both fifth and sixth gears are overdrive gears, with a sixth-gear ratio of 0.67:1.
Gear changes from second to sixth gears are accomplished with clutch-to-clutch control, with the oncoming clutch engaged and the off-going clutch released in a precise manner to achieve the ratio change. The first-to-second upshift is a freewheeling action, where the second gear clutch engages while the first gear one-way clutch spins freely. This allows a greater degree of smoothness at lower vehicle speeds. The clutch-to-clutch shifting and single freewheeler allow significant reductions in packaging requirements.
For severe use, DEXRON VI fluid changes are the only maintenance recommended. For normal use there is no scheduled fluid change.
Source: http://publish.media.gm.com/content/media/us/en/news/news_detail.brand_gm.html/content/Pages/news/us/en/2010/Feb/10chicago/0210_vortec
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