RV Towing In 2011 GM Heavy-Duty Trucks Just Got More Powerful

June 6, 2010/Steve Tackett

MOTOR MATTERS ROLLING HOMES BY JEFF JOHNSTON

General Motors has launched its new 2011 Chevrolet Silverado and GMC Sierra heavy-duty 2500 and 3500 series trucks and the news is good for those who tow heavy RV trailers. The new GM trucks are all about performance improvements that should have RVers excited.
First, what’s not new: The truck interiors are mostly carryover except for a few tweaks and details. GMC has added a Denali trim level model to its pickup line and that vehicle features an interior that shares components and design with the Denali SUV. The truck exteriors feature a new “power dome” hood, new front fascia details and front bumper, but the rest of the exterior is carryover.
On the other hand, an all-new chassis, a revamped 6.6-L Duramax turbo-diesel engine and upgraded tow and payload ratings bump the truck’s performance potential to the next level.
The new 2011 GM trucks can be rated to tow as much as a 21,700 pound fifth-wheel and a 17,000-pound conventional trailer. The trucks can have a Gross Combination Weight Rating as high as 29,200 pounds, properly equipped of course. Slide-in truck camper fans will likely be pleased to know the Silverado and Sierra HD’s new maximum payload has been boosted to 6,635 pounds, and that’s good news given the size of some campers on the market.
Equally exciting, and a component that falls into the “it’s about darn time” category, is an exhaust brake that comes standard with the diesel engine. While aftermarket exhaust brakes typically use a butterfly-type valve that partially blocks airflow in the exhaust pipe, GM employs variable vane technology in the turbocharger to accomplish the same task. The exhaust brake works with the 6-speed Allison transmission’s grade-holding feature and makes running downhill with a heavy trailer far safer and less stressful.
The Duramax is now rated at 397 horsepower and 765 ft.-lb. of torque.

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It uses urea-based Diesel Exhaust Fluid injection to meet the current federal diesel emission standards. An underhood fluid fill receptacle leads to a frame-mounted DEF tank that should, per GM’s estimates, only require refilling once every several thousand miles of travel, depending on load and driving habits.
Changes to the Duramax include a new 30,000-psi piezo-actuated fuel injection system, lubrication improvements, higher-strength pistons and an EGR cooler bypass to reduce high-mileage soot deposits. The net result is a quieter, more fuel efficient and more durable engine. A new larger fuel tank contributes towards a potential 680-mile driving range between fillips.
The new frame is fully boxed, with hydroformed components, and is said to feature a 92 percent bending stiffness increase, plus a 125-pecent stiffer front frame structure. All-new independent front suspension is complemented by new asymmetrical rear leaf springs designed to minimize axle hop and enhance traction control.
Hill start assist, trailer sway control, automatic grade braking and intelligent brake assist are incorporated into the Heavy-Duty truck’s vehicle dynamics electronics.
Our brief driving time with the new GM trucks covered a variety of highways in the rolling hills of western Maryland, which gave us the chance to experience both the uphill power and downhill braking features. Our payload trailer weighed around 9,000 pounds so it wasn’t a major strain on the truck’s tow rating.
The new Duramax is very quiet.

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Changes in the engine along with sound attenuating materials help craft a quiet, civilized driving experience that changes minimally when you put your foot in it to accelerate or climb a grade.
As for fuel economy, we averaged around 9 mpg towing, and about 18 mpg, tops, running solo. This was mainly up or downgrade, with scant level ground running, so flat-ground freeway driving would likely improve those numbers.
We powered up grades at freeway speed, when appropriate, and were able to accelerate up backroad grades in the 7- to 8-percent range after starting at 25-30 mph at the bottom. That’s a good feeling. Cornering and handling are tight and precise. We never felt we had to keep chasing the lane, even when crosswinds were gusting.
The standard GM integrated brake control provided well-balanced brake action between the truck and trailer. Downgrades with the transmission’s two/haul punched in and the exhaust brake engaged called for minimal service brake use to drag us down to a safe speed. We like that kind of confidence in the hills when things get hairy on the road.
Cleaner emissions, decent fuel economy, a civilized ride and power to spare add up to the GM HD trucks being a fine option for heavy RV trailer towing. Pricing for the 2011 Silverado and Sierra start at $27,965. — Jeff Johnston, Motor Matters

Copyright, Motor Matters, 2010

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