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GMC Sierra Heavy Dutys get the job done

September 30, 2005|by TIM SPELL/Motor Matters

GMC's diesel-powered, 4x4 Sierra 2500 Heavy Duty Crew Cab is in its element hauling lumber through East Texas. The mission is a camp project, and the 2005 Sierra is just one of an army of big pickups roaming the Piney Woods.

Rolling through towns where many make their living at sawmills or cutting and hauling timber, the Sierra is accompanied by equipment or wood-laden, diesel-powered trucks doing what heavy-duty trucks are bred for - workhorse duties.

Base priced at $40,790, plus $6,805 for the Duramax diesel with an Allison five-speed automatic transmission, this Sierra SLT is a formidable work truck.

At the stop to load the bed with plywood sheets and 12-foot-long boards, I drop the tailgate to extend the load surface to 8-feet-plus. There's another hauling advantage - the test-truck is fitted with a bed extender. This $210 option is a pivoting, bowed aluminum-tube cage-type unit. It sits in the cargo box with the tailgate up and flops onto the dropped tailgate.

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I start to lift the extender so the lumber-yard hand could slide in the plywood, but he has other ideas. He explains the extender top works excellently to prop long boards on, then setting the plywood sheets on top of them secures the load. The tubes also make great tie-down points for long objects.

If cargo is on the heavy side, the Sierra has the payload capacity to handle 3,570 pounds. This comes courtesy of a sturdy frame and suspension, and the grunt of the Duramax 6.6-liter turbo-diesel V-8 engine. Towing capacity with this engine and a 3.73 axle is 12,000 pounds and climbs to 16,200 pounds with a fifth-wheel or gooseneck hitch and 4.10 axle. The Duramax's output is 310 horsepower at 3,000 rpm and a whopping 605 lbs.-ft. of torque at 1,600 rpm.

GM recently announced there will be more power to feed the demands of truckers. For 2006, GMC is upping the ante with a re-engineered Duramax 6600 turbo-diesel V-8 engine, set to debut as an option on Sierra HD models in the interim '06 model year.

Paired with an all-new Allison 1000 six-speed automatic transmission, the new engine generates more horsepower - 360 horsepower at 3,000 rpm - and has a torque increase to 650 lbs.-ft. GM reports the boosted output comes with lower emissions, and improved quietness and smoothness.

While the '05 Duramax definitely lets you know it's a diesel, the noise level isn't obnoxious and it runs smoothly. Unfortunately, diesel-fuel prices have risen with gasoline prices. There are no published fuel economy figures for the Duramax-powered Sierra, but a rough estimate is 15 miles per gallon, city, and 17 mpg, highway. At least the truck's 34-gallon tank buys a bit more time between fuel stops, which increasingly are becoming more painful experiences.

GM boasts the new-for-'06 Allison six-speed automatic contributes to improved fuel economy and powertrain quietness. The transmission's new tap-shift range selection function also gives the driver more control. This technology pays off in demanding situations, such as trailer towing on a steep grade, by allowing the selection of optimum gears to match the driving conditions.

Inside the test truck's well-insulated, upscale cabin, the diesel sound creeps in only when the windows are down or the power sunroof is open. This sunroof option, which adds $1,100 to the price, tilts and powers to a 13.25-by-28.24-inch opening.

I generally keep the sunroof closed and its shade pulled to escape the viscous summer heat. A big aid to keeping the big cab cooled is the dual-zone air-conditioning system, which comes standard with the SLT model.

This sealed cab also makes for unhindered listening to the XM Satellite radio, a $325 option offering 130 channels. For the ride through East Texas woods, I stick with a few XM country music stations - America, Nashville and Hank's - that, like the Sierra, naturally blend with the setting.

(Tim Spell is automotive writer for the Houston Chronicle Cars & Trucks section.)

Copyright, Motor Matters, 2005

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