3/1/2001 | 6 MINUTE READ

Sibling Rivalry

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Even though midsize SUV sales dipped a bit in 2000, it is a segment that every maker wants to dominate thanks to the monster profits they generate. In 2001, Ford will try to maintain its sales leadership with the introduction of its new Explorer, and Toyota will launch its second assault on the segment with its Camry-based Highlander. Into this competitive landscape steps GM with three totally re-engineered products—the Chevrolet Trailblazer, the GMC Envoy and the Oldsmobile Bravada.

As GM's design and engineering teams began contemplating the form the new SUVs would take, they were faced with many competing demands from consumers (better ride, more power, and increased cargo space) and from the federal government (ever-stricter crash standards). GM also needed to differentiate the styling of the SUV siblings enough to drive a stake in the heart of its cookie-cutter design practices of the past. With the help of smart design and packaging ideas, and the strategic use of proven manufacturing technology, the General met all of its goals and created three highly competitive vehicles.

The I's Have It

GMC Envoy

The new SUVs are equipped with a new engine, dubbed the "Vortec 4200." After considering all of the requirements that the new engine would have to meet, GM Powertrain took the unusual step of green lighting a 4.2-liter, inline six in a market dominated by V8s. Ron Kociba, chief engineer for the I6, explains the decision this way, "We knew that an inline configuration, by nature of its simplicity, was the very best solution. You get one cylinder head rather than two, two cams rather than four, one cam drive system rather than two and so on." Largely due to this simpler design, the Vortec 4200 has 27% fewer parts than its predecessor while far outstripping it in performance. GM's current midsize SUVs are powered by a 4.3 liter V-6 that generates 190 hp horsepower and 250 lb.-ft. of torque. The new I6 makes 270 hp and 275 lb.-ft. of torque. This marked improvement puts the I6 in V8 territory—in fact, the V8 that powers the Ford Explorer has 30 less horsepower and only 5 more lb.-ft. of torque.

Since the Vortec 4200 was a clean-sheet design, Kociba and his team were able to incorporate innovative features that would have been difficult or impossible to do with an existing engine. One such feature is the oil pan axle configuration that has the four-wheel drive differential bolted directly to the oil pan instead of to the frame. The half-shaft passes through a cast-in passage in the pan instead of crossing underneath the pan. This setup allows GM to make the engine lower to the ground which pays dividends in better engine packaging, better visibility, increased styling options and—at a time when the specter of vehicle rollovers haunts SUV makers—it lowers the center of gravity. It also helps to achieve a quieter cabin by eliminating a noise transmission path. The architecture of the Vortec 4200 is so different from GM's current engine line-up (the last time GM equipped one of its vehicles in the U.S. with an I6 was in 1985) that the company built a new plant to manufacture it—Flint Engine South in Flint, Michigan. GM claims that this new plant employs the most accurate precision machining equipment in the world and is flexible enough to build four or five-cylinder versions of the I6 without major modifications.

Seeking Stiffness

Oldsmobile Bravada
Oldsmobile Bravada

GM also took a clean-sheet approach to the frame in an effort to achieve class-leading stiffness and thus reduce NVH to a minimum. The triplets boast the first fully hydroformed frame side rails on a truck. This process, performed by the Budd Company at its plant in Kitchener, Canada, and first used on the Corvette C5, allows the frame to be both lighter and more precisely formed. (GM figures a non-hydroformed frame of similar stiffness would weigh 20% more.) Because the side rails are made with greater precision, fewer parts are welded to the frame; consequently structural rigidity and frame strength are increased. The complex shapes of the side rails are all formed in the same process, including the holes and rail compressions that act as crush initiators and absorb energy from vehicle collisions. GM also equipped its SUVs with eight welded cross-members instead of the usual four or six, which helps the vehicle achieve 260% better torsional rigidity than its predecessor. All of this translates into a trio of trucks with structural stiffness that, according to GM, rival the world's best performance sedans.

Why Did the Assembly Plant Cross the Road?

Final assembly for the triplets will be done at GM's Moraine, Ohio, facility where a new general assembly plant has been built. In preparation for the production of the SUVs, Moraine went through a process that assistant vehicle line executive Rick Spina likens to a child's sliding tile game. Space for renovation was created by sliding whole production departments into other areas. For example, the trim department actually moved across the road while the space it once occupied was re-worked. This allowed production of current models to continue while the plant was being overhauled. GM's goal is to reduce costly downtime between the old and new models, and the company is on target, having shut down for only 2-1/2 weeks to make final preparations before mass production started.

Chevrolet TrailBlazer
Chevrolet TrailBlazer

Spina explains that Moraine has been reorganized to better accommodate the team conept of manufacturing. Each line worker is now a member of a team of between eight and 20 people that is responsible for the quality of its own work. Even the conveyor at Moraine has been split into smaller team-sized sections. The upshot of this new system is less reliance on repair workers to catch mistakes and a more efficient flow of work. According to GM's calculations, the improvements (and some outsourcing) have led to a 20% reduction in total manhours needed to produce a vehicle.

Cookies? No, Thanks

So how about GM's infamous cookie-cutter design tendencies? Well, to extend the confectionary metaphor, the proof is in the pudding. The designers for each of the divisions represented by the triplets have succeeded in differentiating their vehicles largely by making more than 70% of the exterior panels exclusive to each model. But the designers and engineers also did things like giving each of the vehicles an instrument panel that is unique to its division while using the same assembly and connection points for ease of manufacture.

While all three SUVs share similar ride and handling characteristics, the Envoy is arguably the best styled. Its huge front grille and muscular stance scream "Truck!" to an affluent market segment that currently dotes on the appearance of ruggedness. The TrailBlazer's softer evolutionary styling should help it secure a chunk of the larger but less well-to-do SUV market. The Bravada is a different story. Oldsmobile's designers say they wanted the Bravada to look at home when it is side by side with another Olds product. To achieve this dubious goal, they have essentially grafted the front end of an Aurora onto a truck body. Apparently, Olds thinks there are many customers out there who want their truck to look like their sedan and vice versa. If that's so, Oldsmobile will only have a short time to find out . . .


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