Why tamper with success?

Tractor dry weight: 18,370 lbs.
Wheelbase: 273 in.
BBC: 131 in.
Engine: 550-hp Cummins ISX
Transmission: Fuller RTLO20918B
Clutch: Eaton Fuller
15.5 ceramic
Front axle: Dana E1202W,
rated at 12,000 lbs.
Rear axle: Dana DSH40, rated at 40,000 lbs.
Rear axle ratio: 3.70
Tires: Front, Bridgestone R287, 295/75R22.5; rear: Bridgestone M726EL, 295/75R22.5
Wheels: Peterbilt 22.5 x 8.25 polished aluminum
Brakes: 16.5 x 7 cam; front, Bendix lube-free disc; rear, 16.5 x 7 cam
Suspension: Front, taper leaf; rear, Peterbilt low air leaf
Turning diameter right, 36.2 ft.; left, 43.4 ft.
Fifth wheel: Holland, with 36.7-in. air-operated slide
Steering: TRW TAS65
Fuel capacity: Twin 150-gal. tanks
Other items: Hogebuilt stainless steel quarter fenders, remote keyless entry, Platinum interior package, 70-in. Ultracab sleeper, Sirius satellite radio, Peterbilt navigation system, Denso 130-amp alternator, Mitsubishi starter

The more things change, the more they stay the same. In the world of trucking, no product better demonstrates that adage than the Peterbilt Model 389, introduced at the 2006 Mid-America Trucking Show and available in January 2007.

Roughly 99 percent of the 389 is composed of parts taken directly from its predecessor, the Model 379, a legendary truck that’s been in production for 20 years and relatively unchanged during that time. The 379 itself was something of a clone, an upgraded version of the Model 359, which had been Peterbilt’s flagship vehicle between 1966 and 1986.

With a stylistic lineage that dates back to the Johnson administration, the 379 has long been a favorite of owner-operators enamored of traditional squarish hoods, big West Coast bumpers and smaller (i.e. “cozy”) cabs. The truck’s top resale price bears out its ongoing popularity among those who value aesthetics over aerodynamics.

Given this impressive history of marketing success, one might wonder why Pete ever would retire the 379. The decision came after the U.S. Environmental Protection Agency announced new diesel emissions mandates for 2007, says Scott Newhouse, Peterbilt’s assistant chief engineer.

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“A few years ago, when we learned about the heat-rejection requirements of the ’07 engines, we knew that we’d need a new cooling system and improved airflow under the hood,” Newhouse says. “We looked at this as an opportunity to give our customers something extra, not simply add equipment, weight and cost to make the trucks compliant with the new rules. We focused on areas that would add value, to help fuel economy and boost driver comfort and productivity.”

At first glance, the 389 is a 379 with Calvin Klein headlights. Looking closer, Pete enthusiasts will notice that the hood is longer, the grille crown is slightly beveled with larger corner radii, the sun visor is contoured, the grille and air cleaner screens feature a punched oval pattern (first used on the Model 379X, introduced in 2003), the hood ornament is more streamlined, and the front edges of the tool and battery boxes have rounded fronts. Inside, a Peterbilt-specific driver information display and Lowrance touch-screen GPS unit occupy the dashboard’s A and B panels, respectively.

I recently had an opportunity to test a 389 on a short lap of rural Texas, from Denton to Sherman to Greenville and back to Denton. My route, across terrain as flat as Nebraska, was no challenge for the 550-hp Cummins ISX and presented no logical reason to put the Fuller 18-speed through all its ratios – even though the truck was loaded to nearly the legal limit.

Some stretches of the mostly two-lane road I followed, however, did provide a good demonstration of the chassis and cab suspensions. Together, they delivered a ride that was firm yet comfortable. It had a classic Peterbilt feel, which is neither harsh nor mushy.

I spent the first 40 or 50 miles getting accustomed to that vast aluminum acreage directly ahead of the windshield. The 389 is 4 inches longer than the 379, boosting the bumper to back of cab dimension from 127 inches to 131. This change was necessary to accommodate the various emissions components required on engines built after Jan. 1. Truckers wanting a shorter traditional Pete will have to settle for the Model 388 – its BBC is a mere 123 inches.

The extended hood on the 389 certainly will be popular with “large car” aficionados. Although it makes a bold statement, it also obscures sight of the road for the first 34 feet in front of the bumper – 28 inches more than a 379 extended hood – even without a bug deflector mounted to the grille crown.

The 389’s mammoth snout tips with little effort. Engineers redesigned the hood’s spring geometry to make opening and closing as easy as possible, Newhouse says. They also added a locking mechanism – first deployed last year on the Model 386 – to secure the hood in its open position, which is now a full 90 degrees from closed.

My daytime trip in the fire-engine-red 389 provided no opportunity to observe the newly designed headlamps in action. According to the truck’s marketing material, the pair “increases light on the road by 226 percent over previous sealed-beam designs.” The effect is similar to that of high-intensity-discharge lighting used on some European cars, Newhouse says.

“We’re still using halogen bulbs,” he says, “but our designers have fine-tuned the lens optics to throw more light that’s crisper, or whiter, than we’ve had in the past. The better quality of illumination will reduce strain on drivers’ eyes.”

Another strain reducer is the optional factory-installed GPS unit. I became dependent on the device within an hour, constantly checking it for the names of upcoming towns and crossroads long before their signs came into view. Like all such units, this one will either track the vehicle’s movements or display real-time directions to a destination. It also is programmable to include repeat routes and favorite stops, such as Waffle Houses or outlet malls. Equally important, it’s easy to see, mounted in the middle of the B panel, and reasonably simple to operate using touch-screen commands.

Complementing the GPS unit is a new proprietary driver information display, located above the speedometer and tachometer on the A panel. This digital readout shows present and historic stats – fuel economy, trip length, engine conditions, service intervals and more. Some of the display’s numerous menus are deactivated when the truck is moving.

Had I used the system to monitor fuel mileage, I would have impressed no one with my mpg because I mistakenly chose routes notable for stoplights, traffic and 90-degree corners.

It’s difficult to predict how efficiently the 389 will run on a sparsely populated freeway. Although the truck isn’t aerodynamic per se, it’s slightly more “slippery” – 2.4 percent more – than the 379. In theory, this improvement should translate to a 1.2 percent fuel economy gain.

This might be academic to typical buyers, though, who are not choosing a square hood for its ability to slice cleanly through the wind. They’re seeking gratification, the sort derived from running equipment that turns heads and generates pride and envy.

Since the mid-’60s, Peterbilt executives have recognized the allure of their premium owner-operator models, the 359 and 379. They’ve done well during the past four decades, incrementally updating the trucks to stay current with technology and driver comfort while maintaining an unapologetically traditional style. The same is true of the 389, which is more refined yet much the same as its iconic forbears.

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