  AMERICAN MUSCLE  GM’s Heavy Duty pickups; new bodies, more power, same bones
By Bruce W. Smith These old bones ain’t what they used to be. That’s going to be your first impression when you get that first close look of a 2007 GM Heavy Duty pickup—be that a Chevrolet or GMC, two-wheel-drive or four, long bed or short, Regular Cab, Extended Cab or Crew. But in reality, the bones really are the same. It’s everything else attached to the frame rails of the last models of GM truck line to get the major make-over that have changed. The bodies are all-new; the engines have more power; there’s a new transmission; and the handling is much more refined. That’s our take while powering past slower traffic headed up a long, steep grade in the mountains just East of San Diego. Even though there’s a 26-foot, 5,400-pound Ranger center-console fishing boat latched to the hitch, the 2500 Crew Cab 4x4 I’m driving doesn’t flinch. Roll into the throttle ever so slightly and the speedometer needle in the new dash climbs at a very satisfying pace—obviously a direct result of having 660-foot-pounds of torque rolling off the crankshaft of the 6.6L Duramax V8 diesel humming from beneath the new bodywork. Back off the throttle and the Silverado I’m sharing cab time with two others settles down to a smooth, steady, quiet cruise. Gary White, GM North America vice president and vehicle line executive of full-size trucks and one of my driving partners earlier in the day, said early on that “There’s not a broader, more powerful or more capable lineup of heavy-duty pickups in the industry.” BOLD HARD BODIES His words are not mere marketing hyperbole. Just like the all-new
Silverado and Sierra 1500 Series (half-ton) In recent issues we’ve touted the new bodies and spacious interiors found in GM’s full-size SUVs and half-ton pickups. Those same attributes are found in the ’07 2500/3500s. Every model’s cab is just as nicely laid out and comfortable as you’ll find in the other ’07 GM trucks and SUVs. What remains virtually intact in the Heavy Duty models is the frame; those old bones work well for the application. So, GM left them untouched save for some small changes in the brakes and steering, the latter still being recirculating ball instead of rack-and-pinion as found in the half-tons and SUVs. Externally there are more distinct differences between models and brands—most notably the front ends of the Heavy Duty pickups, which convey a much greater sense of power than their ½-ton counterparts. The new grilles are more open than found on the 1500 Series, the hoods taller and vented, the headlights slightly larger, and the front fenders wider and more rounded– all conveying a broad-shouldered, muscular look. GM has even gone to one-piece stamped fenders for the Duallys. SIX-SPEED SHIFTS But it’s under those sculpted hoods of both the GMC Sierra and Chevy Silverado HDs that really separate the men from the boys in the pickup world. The base engine in the new pickups is the 6.0L Vortec gas V8 with
variable valve timing and other state-of-the-art technology that brings
power output to 353hp and 373 lb/ft of torque. Fuel economy, although not Such fuel numbers—and the feel of a much more powerful engine from a stop—is a direct result of an all-new 6-speed automatic that replaces the 4L80 of yesteryear. The Hydra Matic 6L90 has a stump-moving 4.03:1 Fist gear and a wide, 6.04:1 overall ratio (the 4L80 only had a 3.31:1 spread) – including two overdrive gears – that helps deliver an excellent balance of performance and fuel economy. Just as neat is the new six-speed offers manual gear selection with tap up/tap down shift control, a Tow/Haul mode,and Grade Braking, all which make trailer towing a breeze. DURAMAX IMPROVED But the real driving fun comes when you get the optional ($8,500) diesel package. The new Duramax 6.6L turbo-diesel is the most powerful diesel in the 3/4- and 1-ton pickup market with 365 horsepower and 660 lb.-ft. of torque. GM’s torque monster is also one of the cleanest. My seatmate during one of the towing segments, Charlie Freese, the Executive Director of GM Powertrain and the hands-on-expert of the “new” Duramax, says the upgrades bring it 2010 emissions standards all the while improving fuel economy and power. Its cleanliness is quite evident when you’re following one of the new diesel-powered GMs; there’s not a hint of black smoke, nor are you be assaulted by the smell of unburned diesel fuel. The new Duramax provides a 90-percent reduction in particulate matter and a 50-percent reduction in NOx (compared with current standards), meeting a new federal government mandate. (As of Jan. 1, 2007, all diesel manufacturers are required to meet the new emissions standard.) Freese explains such clean running comes as a direct result of computer-designed combustion chambers to burn the fuel more efficiently—and the incorporation of an ungainly-looking exhaust system that includes a catalytic converter, muffler and particulate filter system all funneled out a very weird-looking tailpipe. He explained the odd-shaped exhaust tip greatly reduces the 800-degree exhaust that blows out the particulate filter when it burns off the soot, or “regenerates,” while you drive down the road. As for the fuel economy, Freese says in general a turbo-diesel such as the Duramax will be about 25-percent more fuel efficient than a comparable gas engine when unburdened and up to 70-percent more fuel-efficient when loaded down and running at higher elevations. As it is insiders say the new Duramax should deliver about 22mpg on the open road (unladen, of course) and close to 15 in the city. Not bad for a truck with a curb weight ranging close to 7,000 pounds. TOWING STRENGTH What hasn’t changed in the powertrain is the renowned Allison 1000
six-speed automatic transmission that is partnered with the Duramax 6.6L
turbo-diesel.The Allison can be manually shifted, has grade-braking, and
other features that allows you to easily select the desired gears to match
driving conditions, such as towing a Speaking of towing, if you need to haul your off-road adventure toys the gas-powered Heavy Duty pickups have a maximum gross combined weight rating (GCWR) of a whopping 18,500 pounds, making the new GMs the segment leader in towing for vehicles with a small-block V-8 gas engine. All of the new Heavy Duty’s are equipped with a 2 ½-inch receiver hitch instead of the more conventional 2-inch found on the ½-tons. That means 4x4 models with the gas engine can pull toy haulers and boats up to 12,400 pounds on the ball without using a weight-distribution hitch. The diesels can tow up to 13,000 pounds, or use a 5th wheel and the HDs can pull trailers weighing up to 16,700 pounds.
Add in the option of getting the Z71 Off-Road package on the 4x4s and you can rest assured that if you are an off-road adventurer who needs a strong, refined truck for work—and an equally strong, yet comfortable toy hauler for those well-earned days off—you’d be hard-pressed to find anything better in 2007. I imagine that’s what the guy in the slow lane is thinking right now as I roll past him with my big Ranger boat casting a quick-moving shadow across the sides of his new F-250 Super Duty.—Bruce W. Smith [Sidebar] 2007 GMC/CHEVROLET HEAVY-DUTY PICKUPS AT A GLANCE o 2500HD (3/4-ton) and 3500HD (one-ton) models o 2WD and 4WD drivetrain in all models o Three cab styles: regular, extended cab, crew cab and crew cab Dually o Three box configurations: standard (6’ 6”); long bed & Dually (8-foot) o Choice of 353hp 6.0L Vortec gas or 365hp 6.6L Duramax diesel engines with six-speed automatic transmissions o Z85 smooth ride suspension or new Z71 Off Road package (4x4 only) o Distinct trim offerings, including two different interiors o Segment-best gross combined weight rating of 18,500 pounds (6.0L) o Segment-best conventional trailer weight rating of 13,000 pounds (6.6L)
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pickups, the 2500 (3/4-ton) and 3500 (1-ton) Series Heavy Duty models have
taken a big step forward in refinement. They are hard-core work/play
trucks that are extremely civilized and well-mannered. 
certified, is said to be in the neighborhood of 18mpg on the highway and
near 14 in town. 
trailer on a steep grade. 
Overall
impressions of the GM’s refreshed and refined heavy duty pickups is they
are one of the sweetest combinations we’ve driven to date.