Heavy-duty truck shoppers tend to care about how much a pickup can pull, how well it stops, and how it feels with a big trailer out back. General Motors just gave the 2027 Chevrolet Silverado HD and GMC Sierra HD a major refresh that touches all three. The headline is a massive new 8.3-liter Duramax diesel V-8. Tow ratings climb, too, and the steering finally moves into the modern era.
- A new 8.3-liter Duramax diesel V-8 called Mongoose makes 555 horsepower and 1230 pound-feet of torque.
- Maximum towing reaches 20,000 pounds with a conventional hitch and 38,000 pounds with a gooseneck setup.
- Electric rack-and-pinion steering and electronic brake boost arrive, and both are firsts for the segment.
Meet the Mongoose Under the Hood
The biggest news sits up front. GM’s new diesel is an 8.3-liter V-8 that the company officially calls Mongoose, and it will be an optional engine on both the Silverado HD and the Sierra HD. As the new flagship engine, it puts out 555 horsepower and 1230 pound-feet of torque. That torque figure is the one that counts when you’re dragging a heavy camper or a loaded equipment trailer up a long grade.
The Mongoose is an optional diesel, so buyers can choose it for their hauling needs rather than treating it as standard equipment across the range.
A Smarter Gas V-8 Joins the Lineup
Not every buyer wants a diesel, and GM kept a gas option in the mix. The updated 6.6-liter V-8 now makes 412 horsepower and 472 pound-feet of torque. It also picks up a new turbo-jet intake manifold that GM tuned specifically for heavy-duty performance.
The gas engine gets better cooling and lubrication under load, too. That’s a sensible focus, since plenty of these trucks spend their working lives pulling something. Both engines pair with an Allison 10-speed automatic transmission, so gas and diesel buyers share the same gearbox.
Tow Ratings Climb Across the Board
More power brings bigger numbers at the hitch. Maximum towing now reaches 20,000 pounds with a conventional trailer hitch. Trucks set up with a gooseneck can pull up to 38,000 pounds, which opens the door to much heavier trailers.
The 2500 tops out at 23,200 pounds, and choosing the crew cab drops that figure to 22,400. Cab and axle choices clearly move the numbers, so it’s smart to match the exact configuration to the trailer you plan to pull before you sign anything.
Steering and Brakes Built for Heavy Loads
The change you might notice most on a daily drive is the steering. GM has dropped the old recirculating-ball setup that’s still found on every other heavy-duty truck and switched to an electrically assisted rack-and-pinion system. GM says the new setup has about 30 percent more power than the outgoing hydraulic system, and it should offer much more precise steering. It’s a first for the segment, and so is the electronic brake-boost system that comes with it.
The brake hardware got an upgrade to match. Front rotors now measure 14.6 inches and are clamped by four-piston calipers, while the rear brakes get updated hardware. The new brakes can take more heat. Combined with a new pedal placement and more linear brake travel, they should help drivers feel more confident when hauling heavy loads.
Plan Your Next Heavy-Duty Truck Around the Launch
GM expects the 2027 Silverado HD and Sierra HD to arrive by the end of the year. Pricing hasn’t been announced yet, though it should come out before the trucks reach showrooms. If you tow for a living or pull a big fifth-wheel on weekends, it makes sense to wait for final pricing and configuration details before committing to a current model. Start by writing down your trailer weight, hitch type and preferred cab style. Then compare those against the new ratings once the full lineup is official. A little homework now can save you from buying too much truck, or worse, not enough.
