At first glance, the 2011 Chevrolet Heavy Duty trucks haven't changed much. The Silverado 2500 I drove for a week looked very much the same as last year's model on the outside and retains the 6.6-liter diesel motor and the Allison transmission.

However, I found that the trucks have hundreds of invisible changes! First, under the hood, horsepower and torque are up dramatically. Last year's ratings were 365 hp and 660 lbs. of torque. This year's ratings are 397 hp and 765 lbs. of torque.

Fuel economy

Surprisingly, fuel economy is 11% better in the new models. This is mostly due to a shift away from exhaust gas recirculation to the use of urea fluid to control exhaust emissions. Because of the use of urea fluid in this year's models to control exhaust emissions, the soot collection chamber needs 75% less frequent regeneration (or burning out). This saves fuel because the burning-out process is accomplished by injecting diesel fuel in the chamber to create the fire. (Regeneration needs to be done approximately every 700 miles.) The urea tank is accessed with a filler tube in the engine compartment; it needs to be refilled only at regular engine servicing intervals (approximately 5,000 miles). High-pressure Piezo fuel injectors are used for greater fuel economy, power and reduced emissions. Engine oil flow is increased for more oil pressure at idle and for faster delivery to the turbo. The engine is now B20 compatible.

The Allison transmission is beefed up with a stronger torque converter, a larger-diameter output shaft and more robust clutches. When the transmission is put into tow mode, the shift points occur at higher rpm, and when I took my foot off the accelerator, the engine began to immediately shift down. That feature along with the standard engine brake helps save brake pads and other brake wear. The Allison transmission also features a race-car-like tap up/tap down feature on the end of the transmission shift lever and a patented elevated idle mode cab warm-up feature. Performance of the Duramax/Allison combination is also improved over previous models with preliminary testing showing 0 to 60 mph in less than 9 sec. and quarter-mile times of less than 16 sec.

I took the truck over to my neighbor who has an identically equipped 2006 model. We ran them side by side and found the new truck is a little bit quieter at idle. When my neighbor drove the truck, he was most impressed by the better brakes! They are larger in diameter and width to deliver smoother, more immediate and confident feeling and performance. Wheel hubs and bearings are larger and complement the new brakes.

 

Standard features

Other new features are a longer wheelbase and a wider track. They complement the heavier, stiffer frame with more cross members. The frames have five times more torsional strength than that of last year's models. New dual front jounce bumpers, shock mounts, hydraulic body mounts and new larger springs and retuned shocks are standard. Also standard is a revised steering system that includes a much larger steering gear, larger power steering pump and linkages. Much of this was done to better accommodate front-mounted snowplows.

The truck has a sway control system that senses the trailer sway and intervenes with braking or less engine power to bring the trailer under control. The truck has hill start assist that is automatically engaged when sensors detect that the vehicle is on a grade of 5% or greater. It holds the brakes for 1.5 sec. or until the gas pedal is pressed, preventing rollback. Cold-weather customers will appreciate the diesel's quick glow plug cycle time, which takes no more than 3 sec. in -20° weather.

Many warnings in the manual advise the owner not to modify the engine, transmission, or emissions control systems. All three are highly computerized and the computers are intertwined with each other. The owner's manual also cautions that idling the engine for long periods of time may cause more soot buildup in the catalytic converter, resulting in more frequent need for regeneration. The manual says that, when regeneration needs to be done, the owner should drive the truck at least 30 mph for more than 20 min. and cautions driving the truck around combustible material at that time due to the extremely high temperatures generated in the exhaust system.

The information center on the dash displays engine hours, fuel range, fuel used and transmission temperatures. It also gives warnings about urea left in the tank and tells when the engine needs regeneration. When the exhaust fluid tank is empty, the engine will go no faster than 55 mph. At the next diesel fuel fill — if the driver neglects to add urea fluid — the top speed will be limited to 4 mph.

 

Likes and dislikes

My favorite features of the truck are the silky smooth engine, paired with the quick “rock solid”shifting of the Allison transmission. The truck cruised at 65 mph at only 1,570 rpm and is capable of more than 20 mpg at highway speeds. The 3.73 rear axle and 18-in. tires are a perfect combination. The truck is heavy — approximately 7,700 lbs. That weight is very helpful when you are pulling heavy loads! The hood of the Chevy truck is lower than that of Ford's new Super Duty, making it easier to work under the hood.

I didn't like the black plastic hood vents in front of the windshield. They were a distraction for me when I was driving the truck. Also, during rapid acceleration from a standing start, there is noticeable turbo lag, something that Ford has cured on its new Super Duty with the Scorpion motor.

Standard price of the 2011 Silverado 2500 4-wd Crew Cab is $38,860. Price of the tested 2011 Silverado 2500 4-wd LT Crew Cab Diesel with Allison automatic transmission is $51,045. To learn about the Silverado HD, visit www.chevy.com/NewSilveradoHD.