FORTUNE — The next chapter of General Motors Co.’s (GM) truck strategy is unfolding with the debut of its heavy-duty pickups, a special vehicle chosen by haulers of big loads or by those towing a large trailer, such as one used to shuttle horses to equestrian events.
In a U.S. Market of roughly 1.7 million full-size pickups sold annually, about a quarter will qualify as heavy duty, meaning they’re specially engineered and equipped for strength. More pricey than regular pickups, they also yield more profit — the reason why GM, Ford Motor (F), and Fiat Chrysler Automobile’s Ram division pursue the business vigorously.
“Our goal with the new Chevrolet Silverado and GMC Sierra HDs was to make a stronger, smarter, more refined truck, one that is more confident on the road across the entire line,” said Jeff Luke, GM’s executive chief engineer of trucks.
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“Confident” is a descriptor seldom used with mainstream cars. Its application becomes instantly clear while driving down a steep mountain grade with a large load or towing a trailer with, say, 15,000 pounds of cargo. Such a vehicle needs additional capability, such as heavy-duty shock absorbers and a transmission that can steadily facilitate a controlled descent.
To illustrate the point, GM engineers brought several of its new heavy duties to the high country near Payson, Ariz. For journalists to test. At an altitude of 5,000 feet, breathing is an effort for engines, just like for humans. One of three engine choices in the 2015 Chevrolet Silverado HD (and on the GMC versions) is the 6.6-liter Duramax Turbodiesel, joined to an Allison 1000 six-speed transmission.
Towing a trailer bearing five tons of iron, the Silverado easily outpaced a Ford Superduty and a Ram Heavy Duty as drivers raced the vehicles from valley floor to the summit. (I suppose Ford and Chrysler engineers could have devised competitions that they would have won.) The most impressive part was the relative ease that all of the competitors handled their loads.
On the descent, the Silverado diesel’s “brake exhaust” — which uses adjustable vanes in the engine’s turbocharger to reverse boost — slowed the transmission. With an occasional tap of the brake and a lower gear on top of the brake exhaust, the Silverado HD actually did convey a “confident” feel. It’s a nifty feature for owners of boats, travel trailers, snowmobiles, and others who need such a vehicle.
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The linchpin of GM’s strategy is the standard Chevrolet Silverado and GMC Sierra full-size pickups, the automaker’s top-selling vehicles, car or truck. The Chevrolet Silverado HD and GMC Sierra HD appeal mostly to a commercial and specialized recreational customer.
The third prong of the strategy is GM’s return later this year to the manufacture of smaller midsize trucks, sold as the Chevrolet Colorado and GMC Canyon. GM, Ford, and Chrysler abandoned midsize trucks, ceding the business to Toyota (TM) and Nissan. Ford and Chrysler so far haven’t said they’re returning to the market for midsize trucks.
A big reason for immense profitability of full-size pickup trucks in the U.S. — and thus dependence on them by GM, Ford, and Chrysler for survival — is the fact that the Japanese automakers haven’t succeeded in denting this business. Sales of the Toyota Tundra and Nissan Titan lag far behind.
But perhaps the penetration of the car market by foreign automakers has taught Detroit a lesson. GM realizes it must defend its stake in full-size trucks without reservation. GM’s new line of heavy duties underscores that realization.