Duramax/Allison Partnership Prove Might is Right
The hiss generated by the high-pressure, variable geometry
|Silverado HD is a truck that's at home towing horses, trailers, boats, and just about anything else that can to be moved. (Photo: Rob Rothwell, Canadian Auto Press)|
turbocharger force-feeding GM's massive 6.6-litre (403 cu-in) Duramax diesel V8 gave my prodigious Silverado 2500HD 4X4 tester the acoustics to match its stunning torque rating of 650 pound-feet. Accompanying the mountain of torque in the new-for-2006, larger Duramax is 360 horsepower. That's the kind of brawn needed to pull 5th wheel homes and horse trailers through mountain passes without holding-up traffic like a cork in a bottle. With so much pulling power at one end and dead weight at the other, an automatic transmission was often the weak link in an otherwise very strong chain. For 2006, GM has hardened the susceptible weak link by bolting a 6-speed Allison-manufactured autobox to the rear of its "bruiser," Vortec 8100 (gas) and Duramax 6600 (diesel) powerplants.
|A real big engine with a real big thirst for diesel. But imagine, what would consumption have been like on a gasoline engine? (Photo: Rob Rothwell, Canadian Auto Press)|
Duramax/Allison partnership is definitely the Silverado highlight this year. The big Duramax was engineered to pump-out segment-leading torque while delivering 15 to 20 percent better fuel economy
than GM's current 6.5-litre turbo diesel, although official figures have yet to be released. During my heavy-footed time behind the wheel, the vehicle's driver information screen displayed an average fuel economy rating of 17.7 litres per 100 kilometres, or 13.3 miles per US gallon. Despite these pocketbook-crushing results, GM claims to be setting new industry standards for fuel efficiency, diesel power and performance in the heavy-duty pickup class with the Duramax 6600.
According to GM, not only is their new "oiler" more efficient than
|Duramax diesel is quieter than before, but a symbol of brute force nevertheless. (Photo: Rob Rothwell, Canadian Auto Press)|
previous GM diesels, it's quieter too. Noise, vibration and harshness (NVH) figures, based on GM literature, are comparable to similar-sized gasoline engines. After spending a week behind the wheel of my tester that included both city-traffic plodding and open highway cruising, I'm not prepared to validate GM's NVH claim. From ignition to shutdown there is no doubt that the Duramax 6600 is drinking diesel; nonetheless I was impressed with the civility of the big workhorse. This engine is a pleasure to administer.
|Cold weather not a problem thanks to new glow plugs in the engine. (Photo: Rob Rothwell, Canadian Auto Press)|
to revised glow plugs, the new Duramax starts instantly. Once underway it pleases with delightful-for-a-diesel operational refinement while delivering abundant power in a smooth, progressive manner - and boy can it kick. I was quite surprised by the Silverado's take-off punch and its no-holds-barred passing ability. After the Allison gearbox takes a moment or two to insert the most suitable cog, the big truck storms ahead with unrelenting ferocity. With a range of six gears and 650 foot-pounds of torque at only 1,600 rpm, there were simply no flat spots in the acceleration continuum to impede the hastening of my tester's 2,668 kg (5,883 lb) curb weight. With shift-points coming at 3,200 rpm when the pedal is on the metal, the more gears available, the better.