Take a look what Roman found in the Colorado Rocky Mountains. We believe these are the 2027 Chevy Silverado HD and 2027 GMC Sierra HD prototypes. The trucks appear largely unchanged from what they look like, but they may be hiding the new rumored 8.3L “MegaMax” turbo-diesel V8 under the hood. Let me explain.
The term “MegaMax” originated here at TFLtruck.com when we first got an anonymous report from a person with insider knowledge of what GM may be developing. It refers to a larger displacement Duramax turbo-diesel V8 in the next iteration of GM’s heavy-duty pickup trucks. This is unofficial and unconfirmed information. It came from a credible source, and this is why we decided to publish something about it in January of 2024.
Now, we video of several prototypes testing near the TFL’s Ike Gauntlettm – the world’s toughest towing test. All of the test trucks are identified by the General Motors LLC U.S. DOT stickers. Most of the test vehicles are pulling heavy gooseneck trailers. Some of the Silverado HD and Sierra HD trucks have mobile diesel exhaust testing sensors attached. This is a large and extensive operation.
We currently cannot verify the power output specifications, but some sources says that up to 600 horsepower and 1,200 lb-ft of torque is possible. If these new GM engines produce 1,200 lb-ft of torque, this would tie the high-output Ford 6.7L PowerStroke V8. Ford’s V8 is rated at 500 horsepower.
Most of the gooseneck trailers we saw have what appear to be heavy steel plates on the bottom. They are hauling some of the other prototype trucks as ballast. We estimate the heaviest trailers we see here between 25,000 – 30,000 lbs. They could be heavier, but there is no way for us to know at this time.
Let’s says that our rumor about the larger 8.3L Duramax V8 is not true. There is still no doubt that these trucks are testing an updated or new diesel powertrain. Is it diesel? Yes, we can hear a distinct turbo-diesel sound from these trucks. Most of the test trucks are wearing Duramax badging.
Take a look at the mobile exhaust testing equipment below. What do you think it’s testing? Is it exhaust opacity testing or NOx testing or both?
Why refer to these as 2027 models? Well, it’s because the official information and order guides for the 2026 HD pickup trucks is already out. This official information does not show any engine or powertrain updates. As such, this change should be happening soon after. We estimate that these are 2027 model that will be available for sale some time in 2026.
Please join Roman and I in the video below for all the details.
