2010 Chicago Auto Show: 2011 Chevrolet Silverado Heavy Duty First Look, Part 2

Our first look at the 2011 Chevrolet Silverado Heavy Duty pickup is so large that we've split it up into two parts to make it easier to find the information and material you want to read first.

Part 1: Introduction, Frame, Suspension and Axle Changes
Part 2: Duramax Diesel, Allison Transmission, Safety Improvements and New Models

New "LML" 6.6-liter Duramax Diesel V-8

It's not just the stronger frame and running gear that support the increased towing and hauling numbers in the 2011 Chevrolet Silverado HD. There's also a revised 6.6-liter Duramax clean diesel that provides a significant bump in horsepower and torque. Unfortunately, GM won't say how much that bump is, as it plays a game of chicken with Ford to see which truck-maker will reveal its power figures for its new diesel engine first. Ford hasn't said what the output of its new 6.7-liter Power Stroke V-8 will be, even though it was revealed last September.

The Duramax V-8, dubbed “LML" internally, is the fourth generation of GM's HD diesel since it was introduced in 2001. Sixty percent of its parts are new, and Duramax chief engineer Gary Arvan said it will be 11 percent more fuel efficient than the previous LMM Duramax.

Update: Feb 11, 2009 4:52 PM
Though there are five RPO codes for Duramax engines produced and improved since 2001 -- LB7, LLY, LBZ, LMM and LML -- Arvan clarified for us that the LBZ Duramax was primarily an update to the LLY's existing controls. That's why the LML is considered the fourth Duramax. 

The fuel economy gain is the result of combined improvements in several areas, including long-spaced intervals between the regeneration of the diesel particulate filter, or DPF, which traps soot that's a byproduct of partially burned diesel so it doesn't pollute the environment. After a while, the DPF gets gummed up with accumulated soot and has to be cleaned out. The only way to do this is to inject metered amounts of diesel fuel into the DPF to burn the soot, like a self-cleaning oven. Each regeneration requires up to seven-tenths of a gallon of diesel fuel. The Duramax also uses a new electronically actuated engine fan that draws less power to accomplish the same amount of cooling as the old mechanical fan.

A new 36-gallon fuel tank extends the driving range of the 2011Silverado HD. It’s standard on long and short box versions. GM promises up to a country-crossing 680-mile range, or about 18.8 mpg.

"Heavy duty trucks aren't required to be tested for fuel economy by the EPA," Mikulec said. "But [for the single rear-wheel] truck, we've measured around 15 mpg in the city and about 24.5 mpg on the highway. We have the numbers to substantiate it, but we don't have to put it on the [window] label. There are some limited cases where at 55 mph at a steady state going around a track, we can get over 30 mpg."

Other notable changes include replacing the old solenoid fuel-injection system with high-pressure 30,000-psi common rail piezo electric injectors, a higher capacity oil pump, revised crank for improved balance, and head gasket improvements have been made for greater quality, reliability and durability. Cylinder pressure ratio remains unchanged at 16-1. The variable geometry one-piece solid-shaft turbo has been marginally tweaked to work optimally with the engine's new performance characteristics.

For improved cold weather breathability, the Duramax uses a new flat-panel cartridge air filter instead of the old round filter. It helps prevent snow ingestion. There's also an improved mass airflow sensor to monitor the intake.

The engine block continues to be gray iron construction, instead of lighter, stronger compacted graphite iron used in the new Ford PSD and planned for GM's indefinitely postponed 4.5-liter V-8 Duramax. The block has been slightly revised with new ribbing structures to reduce noise, vibration and harshness and handling of increased torque levels.

New fast-acting glow plugs are said to promise instant cold starts after just 3 seconds in winter temperatures down to 20 degrees below zero.

The new Duramax is also rated to burn up to B20 biodiesel (80 percent conventional ultra-low-sulfur diesel and 20 percent biodiesel).

“We made a lot of enhancements to make sure the new Duramax is robust with biodiesel,” Arvan said. “The engine uses our latest-generation fuel filter that includes a coalescing filter to trap any water that could be present in the fuel. The downstream injector [behind the exhaust] for DPF regeneration means we also won’t have a worry of oil dilution with B20 fuel from in-engine post-injection [like is used on the LMM diesel]. There’s also additional heating to the fuel circuit so the filter won’t get plugged from old [B20] fuel gelling or waxing.”

The DPF injector is a simple, low-pressure gas injector that squirts diesel into the exhaust stream instead of a high-pressure common rail piezo injector.

Arvan said the new Duramax has been durability tested to the 95th percentile level of customer usage, so it will last up to at least 200,000 miles under those conditions.

Allison 1000 Transmission Improvements

The six-speed Allison automatic transmission bolted to the back of the Duramax also helps improve fuel economy. It can lock up its torque converter (used to transmit engine power to the truck’s transmission) faster and stay locked longer. Think of it as taking some of a manual transmission's inherent fuel economy advantages and applying them to an automatic gearbox. There's also reduced spin losses inside the transmission.

The Allison also features a stronger case and new clutches that are engineered to handle up to a 30-percent increase in torque over today's 660 pounds-feet rating. The output transfer case is now oval instead of round to increase its stiffness from the higher torque levels.

Unlike Ford's all-new 6R140 heavy-duty six-speed automatic, the Allison won't add a similar "Live Drive" power takeoff functionality that can power auxiliary equipment (such as a salt spreader) even if the truck is completely stopped and the torque converter is disconnected to keep the engine from stalling.

New Diesel Exhaust Brake

One of the most significant new features of 2007 that caught both GM and Ford by surprise was Chrysler's introduction of a segment-exclusive factory exhaust brake in its 6.7-liter Cummins diesel, like the ones used by big over-the-road trucks.

An exhaust brake saves on brake and transmission wear by clamping down the engine’s turbo vanes, creating back pressure to engine brake the truck. It also reduces the potential for brake fade during long descents, increasing downhill safety while towing and overall wheel brake life.

The 2011 Silverado now has a standard exhaust brake that, like the Cummins, is activated with the push of a button in the center console. It has four operational modes: tow/haul mode engaged, tow/haul mode disengaged, cruise control on and cruise control off.

"Our goal is to have Silverado drivers [with the Duramax] focus just on the road ahead," said Arvan. "They should be able to set the truck to a certain speed and with tow/haul mode and the exhaust brake, the truck will keep that speed constant without the need for them to apply throttle or hit the brakes."

The exhaust brake was tuned by Allison. It's the transmission that commands the engine to activate it. When cruising through mountainous terrain, tow/haul mode's automatic grade braking combined with the exhaust brake will work together to slow the truck on descents to minimize use of the foot brake. If the vehicle's speed increased when the exhaust brake is activated, the transmission will command a downshift. When the grade levels out, the transmission will either upshift or turn off the exhaust brake to keep the correct speed.

Meets Tougher Emissions

Like Ford's Power Stroke, the Duramax will use selective catalytic reduction, or SCR, and a new high-capacity two-stage exhaust gas recirculation system to scrub nitrogen oxide emissions down to no more than 0.2 grams per horsepower/hour. It's a new EPA requirement as of Jan. 1.

The SCR system uses diesel exhaust fluid, or DEF. The urea-based solution (32.5 percent industrial urea and 67.5 percent deionized water) is held in a 5.3-gallon storage tank and injected as a fine mist into the Duramax’s hot exhaust gases. The heat turns the urea into ammonia that, when combined with a special catalytic converter, breaks down the nitrogen oxide emissions into harmless nitrogen gas and water vapor.

The 2010 Ram Heavy Duty 2500 and 3500 pickup trucks with the 6.7-liter Cummins I-6 diesel don't require DEF. They use a scrubbing solution called an adsorber catalyst that uses precious metals like a catalytic converter to eliminate the pollutant. However, the Ram 3500/4500/5500 commercial cab chassis trucks do use SCR, like GM and Ford.

The DEF refill point for the Silverado HD is mounted under the hood of the engine instead of next to the diesel refueling cap on the side of the cargo box, as it is on the 2011 Super Duty.

Arvan said DEF will need to be replenished about every 5,000 miles, depending on duty cycle. An electric heating element inside the tank will thaw the fluid if it freezes.

"We didn't want to make the DEF tank larger because DEF has a shelf life of only about 12 months," Arvan said.

To ensure that the driver refills the DEF tank, Duramax-equipped trucks will warn the driver when the fluid is down to a 1,000-mile range. A series of start-up warnings — including lights, chimes and messages — will become more frequent until the tank is empty. When the DEF fluid is down to a 100-mile range, the truck will be limited to only 55 mph. As the range declines, so will the vehicle's top speed. If the driver continues to operate the truck with a dry DEF tank, after a final warning and restart, the truck will operate in a “limp home” mode that limits speed to just 5 mph until the tank is refilled.

While some may not like having to deal with another maintenance item like DEF, the SCR system in one enabler in helping the Duramax return better mileage than its predecessor.

Safety Improvements

The 2011 Silverado adds the first application of trailer sway control to GM's full-size pickups. It works using the truck's antilock braking system and integrated trailer brake controller to brake individual wheels on the pickup automatically when it senses dangerous yaw in the rear of the truck from the trailer, which could happen if weight unexpectedly shifts inside the trailer. If the trailer has electric brakes and is connected to the Silverado's 7-pin trailer connector, the truck can also automatically apply the trailer's brakes to stop dangerous sway. TRW is the supplier for the system.

The 2011 Ford Super Duty also introduces trailer sway control, but the feature isn't available in the new Ram HD pickups.

The Silverado also has bigger wheel brakes that have increased from 12.8 inches to 14 inches in diameter and widened from 1.5 inches to 1.57 inches. They feature a larger swept area for better stopping power, and the operating pressures have been changed to provide a firmer feel during application with less pedal travel required. The bigger brakes are a necessary improvement to reach higher gross combined weight ratings across the line.

Another new safety feature can help with hill starts. Hill-hold assist will automatically apply the vehicle's brakes for 1.5 seconds once you lift your foot off the brake when you're on an incline. It's part of the Silverado's integrated trailer brake controller, so it will apply the trailer's brakes, too, if it has electric brakes.

Finally, all single rear-wheel Silverado HD pickups will come standard with GM's StabiliTrak stability and traction control system. Though it's not required on trucks with a gross vehicle weight rating of more than 10,000 pounds, on the GM pickups it will run up to the heaviest 11,600-pound GVWR.

"We're not mandated to have stability control over 10,000 pounds, but we're going it anyway," Mikulec said. "It's the right thing to do."

Interior and Access Improvements

As much change as there is under the Silverado's skin, interior changes are virtually nonexistent. There's available mobile Wi-Fi, USB and Bluetooth wireless connectivity and OnStar 9.0, which can stop the vehicle remotely if it's stolen.

The driver information computer in the instrument panel adds an indicator to let the driver know when the exhaust brake has been activated because the exhaust brake button lacks an LED indicator (Update Feb. 10, 2009 4:24 pm - GM says the exhaust brake button will receive an indicator in the center console. It's a recent change from when we originally saw the truck last year). Unfortunately, there's no real-time fuel economy information available through the computer though average economy is available.

Extended-cab models now feature 170-degree-opening rear access doors for easy access to the back row.

New Models

Chevrolet will also have two brand-new models for its HD Silverado lineup. There will be an SRW crew cab with a 6.5-foot cargo box and a SRW Duramax regular-cab with an 8-foot box with either two-wheel or four-wheel drive.

"The two-wheel-drive Duramax regular-cab truck will probably be one of the fastest pickups that we've ever produced," Mikulec said.

Chassis cab versions will be available only as regular- or crew-cab versions. An extended-cab configuration won't be available.

Summary

Since we've had the opportunity to look at the new heavy-duty pickup truck class that meets new 2010 diesel emissions, we've been very impressed with Ford's and Chrysler's latest rigs. They feature many welcome refinements, and in the case of the Super Duty an all-new, powerful and advanced 6.7-liter diesel engine.

When it comes to functional upgrades, though, you are unlikely to tell from the outside that the Chevrolet Silverado is a massive upgrade over the previous model in capability and construction. And it also has a new diesel engine.

It's unfortunate that GM hit the financial wall it did. Given extra money, the company's execs say they would have preferred these new trucks arrive with significant new usability features, like a sophisticated driver information computer, an all-new interior and new sheet metal. But given the poor situation that GM found itself in, it appears the company has pulled off quite a successful revision to a major part of its vehicle lineup.

"Some people said that there wasn’t going to be a future for trucks. Well, that’s just not true," Luke said. "There are always going to be people that need to work with them, pull horses, move concrete, tow things. You name it, they have to do it. That’s why we’re investing in the heavy-duty trucks and raising the capabilities of the trucks, particularly the 1-ton."

We can't wait to drive the heck out of these trucks this summer when they go on sale.

Part 1: Introduction, Frame, Suspension and Axle Changes