While many C/D staffers were slurping up snails and cold soup at the Paris auto show, I was in the Lone Star State scarfing down barbecue with fried Jell-O chasers and driving heavy-duty pickups, on the occasion of the Texas state fair. It’s truck country—approximately one out of every six full-size pickups currently sold in the U.S. calls Texas home. And it was our first opportunity for a stint—albeit a short one—behind the wheel ofthe 2017 Chevrolet Silverado heavy-duty pickup equipped with a significantly revised and more powerful Duramax 6.6-liter turbocharged diesel V-8.
Rated at 445 horsepower and 910 lb-ft of torque, the revamped Duramax adds 48 horsepower and 145 lb-ft to the numbers produced by last year’s engine. Critically—to Chevrolet’s marketing department, anyway—those numbers put the engine in league with Ford’s 6.7-liter Power Stroke turbo-diesel(currently 440 horsepower, 925 lb-ft) and Ram’s Cummins 6.7-liter inline-six turbo-diesel (currently 385 horsepower, 900 lb-ft in the 3500 with the Aisin transmission). As with all claims of pickup superiority, those numbers are subject to change any minute. And no, there aren’t any EPA fuel-economy figures, since these vehicles exceed the 8500-pound-GVWR ceiling of EPA ratings.
The Strong, Silent Type
Our drive was on a closed course at Texas Motor Speedway, with seat time divided into two segments: lapping the oval in a 3500 crew-cab dualie, and a two-lap sprint through a short autocross circuit (!) in a crew-cab Z71 2500 model. In both instances, the single, undeniable first impression was the distinct lack of noise produced by the revised Duramax. The previous engine, while not necessarily louder than its competitors, exhibited an instantly identifiable diesel clatter that was of a higher pitched, more brittle nature than that of the Cummins and the Power Stroke.
While key noise-abatement features include sound-dampening rocker covers and a full-length, two-piece damped-aluminum/steel oil pan and front cover, it’s likely that the fresh internals also contribute to the diminished clatter. Nearly every internal component has been modified or upgraded in a quest for greater refinement and power, save for the 90-degree layout of the V-8, the 103.0-millimeter bore, the 99.0-millimeter stroke, and the basic architecture of the valvetrain and its associated gear drive.
The “new” side of the parts ledger includes the crankshaft, cylinder heads, pistons, wrist pins, connecting rods, electronically controlled turbocharger and actuator, oil cooler, fuel system, in-house-developed electronic controls, glow plugs, exhaust-gas-recirculation valve, and the exhaust system. More than just a parts swap, the reengineering was a comprehensive program that yielded not only a quieter, more powerful engine but one with enhanced exhaust-braking capability and lower oxides-of-nitrogen and non-methane hydrocarbon emissions (the latter by a claimed 35 percent). Additional improvements cited by Chevrolet include increased capacity for the diesel-exhaust-fluid tank, a stronger cast-iron engine block, and an air-induction hood scoop that helps maintain cooler engine temperatures under load. Even the six-speed Allison automatic transmission was upgraded with an improved torque converter, which also permits a lockup function when appropriate.
Forced to pick four standout technologies offered in the new Duramax, we’d go with the stronger cast-aluminum pistons that incorporate a “remelted” combustion-bowl rim for improved thermal-fatigue properties; the double-layer water jackets in the aluminum cylinder heads that allow more strength and more consistent flow; the closed-loop, microprocessor-controlled glow plugs for faster starts in cold weather; and finally the venturi oil-separator system that diverts a small stream of pressure from the turbocharger, which is then used to separate and collect oil in blow-by gases.
And Down the Straight
To see how the laundry list of upgrades translates to the real world, we hopped into a Silverado 3500HD crew-cab dualie towing a 10,000-pound trailer and headed out onto the lower apron of the Texas Motor Speedway’s oval.
With the truck in tow mode and its exhaust brake activated, we pinned the accelerator, which, after taking a moment for the truck to get on boil, resulted in spinning all four rear tires. Remember, this is with a 10,000-pound trailer connected to the standard 2.0-inch hitch.
Cleverly, the software permitted just enough wheelspin to prevent the engine from coming off boost before stepping in and gently letting it hook up. There was no wiggle at the steering wheel or sideways movement of the vehicle, just solid forward motion. Letting off the accelerator at around 70 mph revealed slightly more aggressive exhaust braking, and there was little need to use the brake pedal before entering the corner. Accelerating from moderate speeds, as one would when passing, was drama-free, although the accelerator-pedal travel is definitely long. And as quiet as the truck sounds from the outside, it’s even quieter in the driver’s seat—the telltale diesel rattle is all but nonexistent.
Next we drove the Silverado 2500HD Z71 Duramax with single rear wheels on a makeshift autocross course in the center of the oval, which was a strange and wonderful experience. Even with the dramatically improved torque of the new diesel acting as our willing partner, it was still a game of momentum. The point, obviously, was to keep the rear end in back, following the trail blazed by the front tires. General Motors’ stability- and traction-control systems are pretty adept, so we never experienced any moments of real leniency, but the electronics did let things get a little loose before stepping in. This truck certainly can handle more dynamically than most drivers will ask of a three-quarter-ton crew-cab pickup. Putting it in the box at the end of the autocross was a cinch for the well-calibrated brakes, despite the inert-feeling pedal.
That’s as much as we could pack into our brief first encounter with the new Duramax. Know that we’ll have a full report on the 2017 Silverado HD—and its GMC Sierra sibling—as soon as we can strap our test equipment to the new trucks. But our initial impressions of the turbocharged 6.6-liter Duramax V-8 are that it’s a quiet and refined technical tour de force. As a side note, make sure to ride the Tiki-Twirl before sampling the fried stick of butter, a traditional State Fair of Texas delicacy, or it’ll have your gut misfiring like one of those GM 5.7-liter diesels from the ’70s.