Who needs 660
pound-feet of torque? Someone who needs to drag 13,000 pounds around, that's
who. And the only 3/4-ton truck that can tackle that job is Chevy's Silverado 2500
HD armed with the optional 6.6-liter Duramax diesel V-8, which TheCarConnection.com drove — and admired — during a recent
test.
Chevy's he-truck edges out the Ford F-250's 6.4-liter Power Stroke
diesel, which has a maximum tow rating of 12,500 pounds and 10 fewer pound-feet
of torque. And it out bench-presses the Dodge Ram 2500 even when that truck is
ordered with the newly available 6.7-liter Cummins turbodiesel. (This new engine
replaces the Ram's old 5.9-liter diesel and produces and impressive, but still
second place, 650 lb-ft of torque.)
Both the Ford and Dodge diesels offer
less peak horsepower, too. The Chevy's Duramax weighs in with a class-leading
365 hp vs. 350 hp each for the F-250's Power Stroke and the Ram's Cummins.
Another unique draw of GM's 3/4-ton truck is the heavy-duty six-speed
Allison 1000 automatic transmission — a mandatory upgrade when you choose the
Duramax diesel engine. This is an incredibly beefy unit designed to stand up to
the frame-twisting output of the Duramax V-8. It also has different gear ratios
designed to take best advantage of the diesel's massive low-end grunt. Since all
660 lb-ft is available at just 1600 rpm, the Allison's first gear ratio is
3.10 (vs. 4.03 for the gas engine's six-speed automatic) while fourth
gear's 1.00 (vs. 1.15). And the final drive ratio with the diesel is 3.73 —
vs. up to 4.10 with the 2500's standard gas-burning 6.0-liter V-8 engine.
The taller gearing keeps the diesel V-8 operating closer to its torque
peak off the line and under hard acceleration or while pulling a heavy load,
while also keeping highway revs (and engine racket) down. In sixth at
70-something mph, the big truck lumbers along quietly with the engine barely
turning a fast idle around 1700 rpm.
