General Motors and Isuzu have teamed up to engineer a modern diesel V-8 for customers with tough jobs, such as towing huge boats. Called Duramax 6600, the new engine boasts turbocharging and intercooling, an aluminum block and heads to save weight, electronically controlled direct fuel injection, and four valves per cylinder.
The Duramax diesel is available in the heavy-duty (HD) version of the Chevrolet Silverado and delivers better fuel economy and torque compared with a 6.0-liter gasoline V-8 rated at the same horsepower. Jam a diesel full of air and you get massive punch at low rpm-in this case 520 ft-lb of torque at 1800 rpm-perfect for yanking wet, heavy boats up long, steep launch ramps.
The Silverado 2500HD trumps its competitors with the new Allison automatic transmission, a five-speed, electronically controlled box with a special towing mode. Tap the shift lever and the torque converter locks up in the top four gears to avoid heat buildup.
The Duramax 6600 starts quickly and spits out no smoke. The potent engine and well-coordinated transmission team up to hustle you from zero to 60 mph in less than 10 seconds.
During our tow test, acceleration proved impressive. We hooked up 3,520 pounds worth of MasterCraft skiboat and trailer and clocked 13.9 seconds to 60 mph. Having five ratios on hand is great for keeping the engine humming near its torque peak. Overdrive diminishes driveline noise and boosts cruising efficiency; we measured a respectable 11 mpg. Ride quality noticeably improved with the boat and trailer in tow.
The surprise at the launch ramp was that the Bridgestone radials had difficulty biting down. Were it not for the pushbutton four-wheel drive, we might still be there.
Stepping up to the HD end of the Chevy lineup is the only way to get a crew cab in a full-size pickup. The interlocking rear-hinged doors on regular pickups simply don’t cut it when the crew is anxious to launch.
| MODEL | Chevy Silverado 2500 HD |
| Engine | 6.6-liter OHV turbo-diesel V-8 |
| Net hp/rpm | 300/3100 |
| Net torque (ft-lb/rpm) | 520/1800 |
| Transmission | 5-speed automatic |
| Suspension Front | control arms, torsion bars |
| Suspension Rear | rigid axle, leaf springs |
| Brakes (front/rear) | disc/disc standard 4-wheel ABS |
| Tires | Bridgestone V-Steel M+S, LT 245/75SR-16 |
| Wheelbase (in.) | 143.5 |
| Length (in.) | 227.7 |
| Width (in.) | 79.7 |
| Height (in.) | 76.5 |
| Curb weight (lbs.) | 6,700 |
| Towing capacity (lbs.) | 12,000 |
| Cargo capacity (max. cu. ft.) | 26.5 |
| Fuel capacity (gal.) | 25.0 |
| 0-60mph acceleration (without/with 3,520-lb. towed load, sec.) | 9.1/13.9 |
| 0-60mph stopping distance (without/with 3,520-lb. towed load, ft.) | 153/216 |
| Observed towing fuel economy (avg. mpg) | 11 |
| Price (as tested) | $41,979 |
LAST WORD. Whether the assignment is work or play, Chevy’s Silverado 2500HD powered by a Duramax diesel V-8 shoulders its task with good spirits.
