GM 8.3L Duramax V8 Turbo Diesel Allegedly Under Development With Tremendous Peak Torque

L5P Duramax 6.6-liter turbo diesel V8 11 photos
Photo: General Motors
2024 Chevrolet Silverado HD2024 Chevrolet Silverado HD2024 Chevrolet Silverado HD2024 Chevrolet Silverado HD2024 Chevrolet Silverado HD2024 Chevrolet Silverado HD2024 Chevrolet Silverado HD2024 Chevrolet Silverado HD2024 Chevrolet Silverado HD2024 Chevrolet Silverado HD
In the full-size truck segment, the Big Three in Detroit offer three distinct V8 turbo diesels. At the very top of the spectrum, the Ford Scorpion 6.7-liter Power Stroke develops up to 500 horsepower and 1,200 pound-feet (1,627 Nm) of torque, whereas the standard version makes do with a respectable 475 horsepower and 1,050 pound-feet (1,424 Nm).
Over at Stellantis, the Ram truck brand relies on the 6.7-liter Cummins ISB inline-six turbo diesel. Similar to crosstown rival Ford, what used to be Chrysler offers the Cummins-developed engine in standard- and high-output flavors. Available in both the 2500 and 3500 series, the S.O. mill belts out 370 horsepower and 850 pound-feet (1,152 Nm).

Leveling up to the H.O. tune, which is exclusive to the 3500, means 400 ponies and 1,075 pound-feet (1,458 Nm). Not surprising in the least, GM ranks dead last in this department with its long-running Duramax V8. Internally referred to as L5P, said engine was improved for model year 2024 in many respects, beginning with new head gaskets and pistons, a new high-pressure fuel pump, thicker fuel rails, and 10 blades for the turbocharger's turbine wheel instead of the 2023 model's 11 blades.

What's more, General Motors upgraded the L5P to the Global B electrical architecture for improved cybersecurity. Be that as it may, the 6.6-liter V8 is rated at 470 horsepower and 975 pound-feet (1,322 Nm). This, in turn, puts GM behind Stellantis and the Ford Motor Company. Rather than accepting the status quo, the Detroit-based automaker is allegedly developing a new Duramax V8 turbo diesel.

Citing a source familiar with powertrain development, The Fast Lane reports that an 8.3-liter colossus may launch around 2026 with impressive output figures. Lovingly nicknamed Megamax by The Fast Lane rather than General Motors, the yet-unconfirmed engine is understood to develop 600 horsepower and 1,200 pound-feet (1,627 Nm).

2024 Chevrolet Silverado HD
Photo: Chevrolet
More power than yet similar torque to the Scorpion Power Stroke sounds plausible, more so if you remember that the 8.3-liter Duramax boasts 1.6 more liters of displacement. Those 1.6 liters also mean a less strained engine, thus meaning – at least in theory – a longer lifespan. The only transmission compatible with said powerplant would be the Ford-GM automatic with 10 forward ratios, which is codenamed 10L by General Motors and 10R by the Ford Motor Company.

GM's beefiest version is the Allison-branded 10L 1000, which is a completely different automatic from the Allison 1000 five-speed transmission. The 10L 1000 can take up to 1,033 pound-feet (1,400 Nm), therefore it requires a few upgrades for this application. General Motors could very well take inspiration from the Ford 10R 140 for upgrading the 10L 1000 to 1,200 pound-feet (1,627 Nm).

Andre Smirnov and Roman Mica highlight that they couldn’t get any confirmation whatsoever from General Motors in regard to the 8.3-liter Duramax, be it official or unofficial channels. It remains to be seen whether a turbo diesel this large makes any sense, though, especially considering the CAFE fuel efficiency standards for model year 2030 through model year 2035 heavy-duty pickup trucks.

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About the author: Mircea Panait
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After a 1:43 scale model of a Ferrari 250 GTO sparked Mircea's interest for cars when he was a kid, an early internship at Top Gear sealed his career path. He's most interested in muscle cars and American trucks, but he takes a passing interest in quirky kei cars as well.
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