Final Link in GM Truck Revamp Gives HD Line a Power Trip
John Clor, Contributor
For automotive journalists, there are two types of press introductions. There are the "oh-boy" ones that are dangled before the staff like raw meat in the lion's den, and the "oh-no" ones that get passed around from desk to desk, carrying more "can't make it" excuses than a baby shower invite on Super Bowl Sunday.
As you'd guess, the "oh-boy" ones usually involve cool cars and exotic locations, or lots of horsepower and track time. And the "oh-no" oneswell, let's just say they're less exciting. So when General Motors sent out invitations to cover the press introduction of its 2001 Heavy-Duty truck lineup in Branson, Mo., you can bet the buff-book boys were tossing it around the office like an errant jockstrap in the sixth-grade boys' locker room.
But not at Edmunds.com. That's because the fact that Americans now buy more new trucks each year than they do cars hasn't been lost on us. We're fully aware that full-size trucks are the best-selling models on the planet. And with three-quarter and one-ton pickups making up roughly a third of the full-size market, we know that these new heavy-duty units are a key element in GM's strategy to overtake Ford in truck sales leadership.
On the heels of Ford's F-Series redesign in 1996 and subsequent rollout of its new Super Duty F-250 and F-350 models, the General had split its own full-size truck rethink into three phases. The first was the 1999 launch of its bread 'n' butter 1500 and 2500 series Chevrolet Silverado and GMC Sierra pickups. That was followed by the full-size sport-utilities, the new 2000 Chevy Tahoe and Suburban, as well as GMC Yukon and Yukon XL. Now it was time to bring out the new 2001 Heavy Duty (HD) Silverado and Sierra.
The full-size segment is expected to ring up some 2 million sales in North America during 2001, with GM hoping to ramp up enough production to capture about 250,000 HD sales before the model year is out. While GM's light-duty pickup duo still trails Ford's F-Series in the sales race, its full-size SUV lineup is currently ahead of Ford's. If these new HD trucks can accomplish the same task, you can see how that might shift the balance of sales power over to General Motors. But just how do they plan to pull that off?
Simple: Give the HD pickup customer exactly what they wantthe ability to do more haulin' or towin' for workin' or playin' hard. GM calls it minding the three "P's"Power, Payload and Pullin'. So that's exactly what they set out to develop: exceptional powertrains, outstanding payload capacity, and unparalleled towing and hauling ability.
Of course, all the 2500 HD (single rear wheel) and 3500 Series (dual rear wheel) 2001 modelsavailable in Regular Cab, four-door Extended Cab, Crew Cab and Chassis Cabare now wrapped in the Heavy Duty versions of the Silverado and Sierra's new sheetmetal. The Chevy gets a bolder, more aggressive front design with a wide, chrome grille and big, gold "bow-tie" emblem. Its GMC sister has a more poised look, with thicker bumper pads beneath a chromed center-port grilleall riding on a chassis that sits 2 inches taller than the Chevy for added stature.
The Crew Cabs boast an all-new four-door cabin that offers more head-, shoulder- and hip-room than the previous generation, and all models get a cargo box that is somewhat longer, wider and deeper, and has more tie-downs, than before. Like the plan for GM itself, the idea with these trucks was to make them bigger, faster, stronger and smarter.
To that end, GM's new HD truck lineup debuts three engines: the all-new 6.6-liter Duramax diesel; the all-new 8.1-liter gas-powered Vortec V8; and an improved 6.0-liter Vortec V8. There are also four transmission offerings, depending on engine choice and model: a new Allison five-speed automatic; a ZF six-speed manual; a beefed-up GM Hydra-Matic 4L80-E four-speed automatic; and a NVG five-speed manual.
Let's start with the baddest of the bunch, the diesel. The Duramax 6600 is an all-new turbodiesel V8 replacing the GM-sourced 6.5-liter turbodiesel in previous HD models. Developed jointly with Isuzu (who, believe it or not, is one of the world's largest diesel engine manufacturers), the 6600 is said to be the most powerful diesel ever produced for a heavy-duty pickup, boasting 300 horsepower and an unimaginable 520 foot-pounds of torque. (That equates to 65 horses and 20 foot-pounds more than Ford's PowerStroke, and 55/15 over the Dodge Cummins diesels.) Not only that, but fuel economy is actually some 15 to 20 percent better than GM's old 6.5-liter diesel.
This new Duramax is an OHV 90-degree V8 with an induction-hardened, deep-skirt block and nitrided crankshaft. It has four valves per cylinder, aluminum high-swirl cylinder heads and a common-rail fuel system featuring Bosch direct-injection. Operating life has been certified to 200,000 miles, and it carries a five-year, 100-000 mile warranty to match Ford.
Beyond this engine's outstanding power-to-weight ratio is easy serviceability that has been engineered-in. Its compact size (both shorter and narrower than competitors' diesels) means there's more room under the hood, especially with the turbocharger being located in the "vee" space atop the engine and not off to the side. That means easier access to the engine's external components, including the oil and fuel filters.
Some of the cooling advancements for this powertrain include a new charge-air cooler, an integral oil cooler, a piston-spray cooling system, a transmission oil cooler, and a big 21-inch-diameter composite engine fan with large modulating clutch and a two-piece fan shroud. All of this means the Duramax should keep its cool during even the most demanding towing or hauling tasks. The new engine is being built at a new GM/Isuzu joint-venture facility in Moraine, Ohio, called DMAX, Ltd.
If gasoline power is your thing, GM offers the most powerful gas engine in the HD marketthe all-new Vortec 8100 V8. Replacing the 7.4-liter V8, the 8.1 offers 340 horsepower and 455 foot-pounds of torque while delivering a 4 percent improvement in fuel economy. The output of this new engine actually exceeds that of the V10s being offered by GM's competitors. Both the Dodge 8.0-liter V10 and Ford 6.8-liter V10 make 310 horses, with the Mopar churning out 450 foot-pounds of torque and the Ford 425.
That power advantage means better acceleration across the entire load range. In GM tests, the new Vortec V8 ran its 7,200-pound load zero-to-60 mph in 9.1 seconds, compared to 10.2 seconds for the Dodge V10, and 10.9 for the Ford V10. And the differences are even more dramatic when sprints are measured under a full 22,000-pound load. Indeed, in uphill pulling tests set up for us, the GM engines outran their competitors to the top of the hill every timeand actually gained more ground as the incline got steeper.
The heritage (not to mention the bore-center dimension) of the new 8.1 dates all the way back to the 348 cubic-inch "Big Block" of 1958. But that's where the similarity ends. This thoroughly modern mill features a coil-near-plug ignition, an engine oil life monitor, a coolant loss-protection system, and even a dual-belt accessory drive for reliability. And pieces such as a nodular-iron balanced crankshaft and stainless-steel exhaust manifolds help the Vortec 8100 attain a 200,000-mile operating life durability rating.
Last but not least, powertrain engineers even decided to upgrade the nearly new Vortec 6000 V8, which was introduced in GM's redesigned light-duty pickups that debuted in '99. More than 10 improvements, such as new aluminum cylinder heads similar to those used on the LS6 Corvette, a new steel camshaft, and revised intake manifoldhelp the revamped 6.0-liter make 300 horses and 360 foot-pounds of torqueboth class-leading numbers for the standard V8 offering. With Ford's 5.4-liter Triton motor making 260/350, and Dodge's 5.9-liter Magnum managing 245/345, GM has upped the ante on power across the board.
The base Vortec features an oil change interval that is now up to 10,000 miles, and has also attained GM's 200,000-mile durability rating. And it can be had with either GM's newly beefed-up Hydra-Matic 4L80-E four-speed automatic transmission or the NVG (New Venture Gear) five-speed manual. Opt for the big gas or diesel motor, and you get two other trans choices, either the five-speed Allison automatic or a ZF six-speed manual.
We'll admit to being quite impressed with the Allison, a name we recognized from the medium-duty truck market. (About 80 percent of the automatic transmissions installed in all makes of medium-duty trucks built today are supplied by Allison.) GM chose Allison because none of its current automatics were rated to handle the 520 foot-pounds of torque generated by the new Duramax 6.6 turbodiesel. This transmission is rated at 19,850 GVW and 26,000 GCVWboth of those commercial-use standards that are far beyond the capability of even these new GM trucks.
But besides its stout launch feel and nicely spaced gear ratios, the electronically controlled Allison offers "grade braking" as well as a bolt-on "Power Take Off" feature that allows owners to run PTO-driven equipment on-site, delivering 250 foot-pounds of continuous torque via IP-mounted PTO controls. We found that its patented grade braking capability is an immense help when towing big and heavy trailers to keep the truck under control on steep grades and avoid overheating the brakes. By automatically finding the optimum gear ratio to supply downhill engine braking without manually downshifting, the Allison takes the guesswork and stress out of towing in hilly terrain.
For our money, the Allison is the way to go on any of these big rigseven for you old-schoolers who think the only way to get driveline durability is to go with a manual gearbox. Plus, it makes hauling and towing big loads much less of a chore. The grade braking feature allows you to concentrate on the road instead of gear selection, and its "shift stabilization" feature prevents ill-timed upshifts and downshifts, as well as smooths out the driveline jarring than can occur under hard acceleration under load.
But to make these new powertrains work properly, GM had to redesign the HD series trucks from the ground-up: Enter an all-new chassis built to meet new strength and durability limits as well as the needs of body upfitters in the commercial market.
All 2500HD, 3500 Pickup and 3500 Chassis Cab trucks now tout a new multi-section modular frame, with more rigid 'hydro-formed" front section to improve front-end alignment and body fits. The frame rails on the Chassis Cab trucks are thicker and deeper in high-stress areas. These new frames give best-in-class Gross Vehicle Weight (GVW) ratings of 9,200 pounds for 2500HD trucks; 11,400 for 3500 2/4WD dually models; 11,400 for the Chassis Cab 2WD dually; and 12,000 for Chassis Cab 4WD dually.
A revamped torsion-bar front suspension is now employed on both two- and four-wheel-drive models, giving added durability to the 2WD trucks. In addition, the front axle capacity has been increased to 4800 pounds, with the payload capacity of the rear leaf-spring/live axle suspension boosted to 8,600 pounds. You get a choice of two different rear axles, either a 10½-inch ring gear axle with a 6,900-pound maximum rating, or an 11½-inch ring gear axle that carries a maximum rating of 10,000 pounds.
In order to keep the trucks out on the job longer, fuel capacity has been expanded. For the 2500HD/3500 Series equipped with the short-box bed (6.5 feet), a 26-gallon fuel tank is standard. The long box (8-foot) versions get a 34-gallon tank. On Chassis Cab models, a 27-gallon primary tank is mounted midship, with a 23-gallon rear-mounted secondary tank available as an option. As you might imagine, driving range gets a big boost with up to 50 gallons of fuel aboard.
To bring this newfound power to a halt, the brakes have been redesigned to provide shorter stopping distances and better pedal feel. For the first time, four-wheel discs are employed on all GM HD pickups. GM's Hydra-Boost system sends stopping force through twin-piston calipers, and now features dynamic rear proportioning, which helps to maximize the rear brakes. The combination of larger front rotors and larger brake pads (a 36 percent increase in pad surface) means a substantial increase in normal brake life.
Naturally, all of this mechanical upgrading means nothing if together it doesn't equate to better pulling ability, for HD trucks and trailering go hand-in-hand (or should we say hitch-in-hitch?) So you just had to know that best-in-class trailer-tow ratings were the goal for GM engineers. And that's exactly what they accomplished. The standard trailer tow rating has been increased by 2,000 pounds to 12,000; for fifth-wheel or "gooseneck" trailers, the HD landed an unprecedented 15,900-pound rating, which is more than a 2,000-pound increase over the previous models; and total Gross Combined Vehicle Weight (GCVW) is now a whopping 22,000 pounds.
Beyond all the raw numbers, engineers told us they targeted a total systems integration approach to the trucks' improved towing ability, combining powertrain, frame, suspension, axles, brakes and fuel systems to all work in concert and enhance the overall towing experience. We might add that with the transmission "tow/haul mode" feature and the newfound "grade braking" ability of the Allison, towing even a large trailer has never been easier.
Because it is such a big part of the ownership experience, most of our considerable drive time with the new HD trucks in and around the Ozark Mountains outside the resort town of Branson involved towing. GM included a variety of towing challenges to pull along on our trip, from huge, fifth-wheel travel-trailer homes to big boat and horse trailersand we actually tried most of them. We found that the Duramax/Allison combination made child's play of even the biggest of loads. Quieter and more seamless than its Ford and Dodge counterparts, this new GM diesel should prove a popular choice.
Of course, power was also appreciated in the Vortec line, but we couldn't help seeking out the new 8.1-liter for a few legs of our drive through the rolling countryside. We found the V8s both eager and responsive, with smooth tip-in when throttling up steep grades. And while we preferred towing with the automatics, even the manual transmission-equipped models we sampled proved easy to operate.
Save for commercial applications, the interiors are much like you'll find in GM's full-size pickups and SUVs. All the trucks that we sampled, both Chevy and GMC, were roomy and comfortable, though nothing beats a Crew Cab when taking along passengers.
Prices were not announced, but GM officials vowed to be very competitive with similar Ford and Dodge offerings. Given how they went after their rivals in establishing new benchmarks for power, torque, efficiency, durability, and capabilitywe don't doubt GM intends to beat them on price as well.
The end result is a top-to-bottom rethink of GM's entire heavy-duty lineup that boasts the most powerful engine offeringsgas or diesel. They've got the highest GVW and payload ratings for both three-quarter and one-ton models. And the most towing and hauling capacity, as well as the highest Gross Combined Vehicle Weight (GCVW) ratingsbar none. When you factor in all the new features of these new trucks, and include a solid dose of real driveability, then you can't help but to think that GM has put together a winning combination here.
While we're not sure that the evolutionary styling of these new GM big rigs carries the brute appeal of a Ford Super Duty or the big-nosed 3500-series Dodge, we do know that GM's new HD duo will easily beat them when it comes to good, ol'-fashioned pullin' and haulin'. And for that, all we can say is more power to 'em.
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