The output is staggering. The 6.6-liter turbodiesel V-8 with the Allison 10-speed automatic transmission makes 445 horsepower and 910 pound-feet of torque at just 1,600 rpm. Unladen, the HD diesel hauls something other than cargo. It’s surprisingly quick in a straight line, moving much more like a light duty than a heavy duty. When equipped with dual rear wheels, optional turbodiesel, and rear-wheel drive, it can tow 35,500 pounds (an increase of 52 percent from the outgoing model). With the gas engine, dual rear wheels, and rear-wheel drive, the Silverado 3500 can carry up to 7,442 pounds in the bed and cab. There’s a giant 28-inch fan to cool the massive diesel engine, and the fan will run for up to 15 minutes even if you kill the engine while it’s still hot.
If you’re going to tinker with that engine, you might need a ladder to access what’s under the vented hood.
The gas model is no slouch, either, though it trails the competition by a small margin. The 6.6-liter V-8 gas engine with 6-speed automatic transmission makes 401 hp and 464 lb-ft of torque at 4,000 rpm.
The cabin is sealed from road and engine noise while cruising, while the independent front suspension and stiffer body smooths out road imperfections, making it a softer, gentler, easier ride. Leaf springs in the rear are more stable when hauling, and bouncy when unladen. Overall, we give it a 5 for being able to haul the heavy load but it handles like the very large truck it is, even if the cabin is quiet.
The differences behind the wheels of the 2500 HD models largely comes down to the transmissions. Towing about 12,000 pounds uphill in the Cascade Mountain range with the gas engine at an altitude of about 7,500 feet, the 6-speed has to hold gears longer and work harder to get the max 464 pound-feet of torque at 4,000 rpm. While coasting on the way down that same grade in tow haul mode, engine braking kept it at about 4,500 rpm until it leveled out.
Pulling a load from a stop is no problem, thanks in part to the higher compression ratio and the increased displacement from 6.0-liters in the outgoing gas model. One hard brake event downhill before a 90-degree turn provided plenty of confidence to do it again.
Even when hauling heavy loads in the gas and diesel models, the tail did not wag the dog and the steering stayed centered on straight roads. Turning from a divided highway to a single lane country lane required a wide berth to prevent the trailer from clipping a corner, but it was relatively easy because the steering stayed true to the intended angle. We even did a turnaround in a horseshoe-shaped parking lot ringed with cars without a problem. And that was our first time hauling such a load.
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