General Motors just dropped a bombshell that’s going to blow up the truck forums: 2027 heavy-duty trucks get an all-new Duramax diesel V-8 with the biggest displacement and highest horsepower and torque numbers in the HD-truck business.
The Big New Duramax
The all-new Duramax ups its displacement by nearly 26 percent to 8.3 liters. That alone is remarkable news, considering the Duramax has been a 6.6-liter engine since GM introduced it more than a quarter-century ago. The new Duramax 8.3 makes peaks of 555 horsepower and 1,230 lb-ft of torque, an increase of 85 hp and 255 lb-ft over today’s Duramax. More important, it tops Ford’s 6.7-liter high-output Power Stroke V-8 by 55 hp and 30 lb-ft and Ram’s 6.7-liter Cummins diesel by 125 hp and 155 lb-ft. Given that massive displacement, we bet the new Duramax has room to grow, too.
GM said this is the first in-house clean-sheet redesign of the Duramax diesel. It features a compacted graphite iron block, forged crankshaft and connecting rods, and steel pistons. The engine, according to GM, is specifically designed not to wither under heavy towing, with a variable-geometry turbocharger, air-to-water intercooler, and cooling-system improvements. If that’s not enough, GM also said the new engine is quieter and more refined than the old 6.6.
Maximum towing capacity remains at 20,000 pounds for conventional trailers but rises by a ton to 38,000 pounds for gooseneck trailers. Although that edges out the 2027 Ram HDs on gooseneck towing by 980 pounds, Ford is still the trailer-towing champ at 40,000 pounds. GM will continue to be behind its cross-town competitors on conventional bumper-pull trailers; Ram and Ford can tow 23,000 and 30,000 pounds, respectively.
Towing capacity is limited not just by engine but by suspension and braking, so we’re not surprised to see only modest changes here. (A disclaimer, not from our lawyers but us, because it’s important: These are maximum numbers, and depending on how a given truck is equipped, it may tow less, potentially a lot less. Always, always, always check the manufacturer’s towing chart for any particular configuration.)
Do Not Pass Go: Steering and Braking Improvements, Too
Although the bigger, burlier Duramax engine is bound to steal the headlines, it’s not the only improvement The General is making to Chevrolet’s and GMC’s heavy-duty pickups—and the other changes are significant enough that we hope they won’t be obscured in a cloud of Duramax exhaust.
First, the base gas engine, a 6.6-liter V-8, gets a slight power bump to 412 hp and 472 lb-ft, up from 401/464 (not that impressive compared to the diesels but still useful).
Second and perhaps most significant is that the HD trucks get a new electric rack-and-pinion power steering system, otherwise known as EPS. Although EPS is all but universal in cars, SUVs, and lighter-duty pickups, HD trucks have stuck with older hydraulic systems. This is, so far as we know, the first application of EPS to a heavy-duty pickup.
What’s the advantage? EPS eliminates the engine-driven hydraulic pump and a lot of plumbing, making the system simpler and lighter. It also consumes less power because, unlike with an engine-driven pump, there’s no parasitic power draw when the system isn’t providing assistance. EPS makes it far less complicated to fit a proper lane centering system, as well, though GM has not announced one for the 2027 trucks. (Ford has lane centering on the Super Duty, which uses a motor on the steering column to provide steering input.) GM said the new EPS system provides more boost, improved on-center feel, and reduced kickback.
New Brake Booster Enables One-Pedal Driving
GM truck fans know the Hydroboost brake booster relies on pressurized power-steering fluid, so that gets an upgrade, as well. 2027 GM HDs get a new electronic brake booster the company said is also an HD pickup first. Paired with larger front brake discs (14.6 inches, up from 14.0), four-piston fixed front calipers, and unspecified upgrades to the rear brakes, GM promised the new system will deliver more braking feel, better thermal capacity, and a repositioned, shorter-travel brake pedal. The new system also allows for better integration with adaptive cruise control and automatic emergency braking.
Another one of the new braking system’s advantages is that it allows one-pedal off-road driving in both four high and four low transmission modes. This feature comes courtesy of a new Terrain driving mode for Chevrolet Silverado 2500 ZR2 and GMC Sierra 2500 AT4X trucks. All versions of the 2027 HD trucks get updated Tow/Haul and Off-Road modes that take advantage of the new steering and braking technologies.
Ready to put that big new Duramax in your driveway? GM said the 2027 trucks will arrive in dealerships toward the end of this year, with pricing and equipment availability announced closer to their on-sale date.
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