General Motors just shared details about the new 8.3-liter Duramax turbodiesel along with the relevant changes being made to the next batch of HD pickup trucks designed to accommodate the massive engine.
Thanks to other manufacturers not doing much beyond showcasing a few pointless concepts and announcing some new paint options this week, General Motors’ evolving engine lineup has taken up the brunt of the automotive news cycle.
We previously discussed the updated (and upsized) V8 motors slated for the 2027 Chevrolet Silverado 1500 and GMC Sierra 1500. But their HD equivalents are also in line to receive a gargantuan-sized diesel the manufacturer had codenamed “Mongoose,” as an indirect way to insult rival powertrains used by Ford Motor Co.
While it’s always fun for fans of the involved brands, any shade throwing approved by the marketing department ultimately doesn’t matter. The true worth of a vehicle rides upon its capabilities, dependability, performance, value for money and how it makes the person driving it feel. But those aren’t things that can be assessed in any meaningful way until the relevant automobiles have spent at least a few years on the road.
In lieu of all that real-world data, having a spec sheet is pretty handy.
“This new diesel engine is the culmination of decades of GM diesel development and integration,” stated Norman Peralta, executive chief engineer, Global Engine and Battery Systems. “From the clean-sheet architecture and combustion system to the cooling, aftertreatment and transmission calibration, this is a powertrain built with heavy duty purpose and pride.”
General Motors promises that the all-new Duramax 8.3-liter turbodiesel V8 (built in Brookville, Ohio) will offer best-in-class diesel horsepower and torque for the HD pickup segment. The new motor offers a claimed 555 horsepower and 1,230 lb-ft of torque.
While those are impressive figures, Ford’s significantly smaller 6.7-liter PowerStroke V8 turbodiesel actually isn’t all that far behind. Most versions offer 475 hp and 1,050 lb-ft at the kind of low engine speeds you’d expect from a diesel. Ram’s Cummins-equipped models also stay competitive, with the 6.7-liter inline 6 turbodiesel boasting a maximum of 430 hp and 1,075 lb-ft. However, the Blue Oval also offers high-output variants of the PowerStroke V8 yielding 500 hp and 1,200 lb-ft of torque.
The above begs the question of how much those numbers actually matter. Customers purchasing a diesel pickup are presumably doing so because they plan on racking up the miles and towing a significant amount of weight on a regular basis. GM stated that the maximum available trailering capability will be up to 20,000 pounds on conventional HD pickups and up to 38,000 pounds gooseneck models. This is certainly an improvement in metrics. But it also won’t be making the Chevy or GMC a class leader in terms of pulling weight. General Motors has effectively just managed to match Ram and will still lag behind Ford’s maximum 40,000 pounds.
But getting tapping into that capability requires spending an excessive amount of money for a truck that’s been specifically designed to to become a junior Class 8 vehicle. A couple thousand pounds presumably won’t matter as much as how well the vehicle holds together under sustained abuse. This is where the 8.3-liter Duramax could actually shine the brightest. By being significantly larger than what’s presently on offer from rival domestic truck manufacturers, GM’s diesel could (theoretically) outlast the competition. Since this is another reason someone would option a diesel motor over something that runs on gasoline, dependability is undoubtedly important to would-be buyers.
But that factor is also completely unknown since this is an entirely new diesel architecture developed by General Motors. Granted, the manufacturer has a pretty good track record when it comes to fielding diesels. But its new line of V8 gassers presumably exist just to put some distance between the last-gen powertrains that were assumed (and sometimes proven) to have reliability issues.
That said, lapsing quality control feels like an issue that’s blighting the entire industry as a whole of late.
Working in the Duramax’s favor is a compacted graphite iron cylinder block along with a fully forged crankshaft, connecting rods and steel pistons. Heat dissipation has also been considered, with there being an OEM dual-stage air-to-water charge cooling system, variable-geometry turbocharger and an “upgraded engine-cooling strategy to help deliver consistent performance when the truck is working hard.”
GM has also stuck with Allison transmissions, which have enjoyed a famously favorable track record for long-term dependability. But the 8.3-liter has been mated to the brand’s newer 10-speed that has previously been criticized by some customers for solenoid issues and not always playing nicely with software updates.
Since emissions controls have likewise been an issue for long-term diesel reliability in general, there were some promises made that the exhaust aftertreatment system had been updated to “support heavy-duty performance, regeneration functionality and customer confidence over long-distance towing.” We have no idea what types of mechanical changes that will entail at this time.
Meanwhile, those that just feel like model diesel compromises aren’t worth it can run with the new gasoline-powered, 6.6-liter V8. With 412 hp and 472 lb-ft of torque on offer, it’s good for towing 16,000-18,700 pounds when properly equipped.
Beyond that, General Motors has said that it has focused its remaining efforts on building an HD pickup that’s comfortable to drive — even when towing a sizable payload. Both the new V8s are alleged to have an extra-meaty torque curve and an all-new electronic brake-boost system that’s supposed to be cutting edge. Larger 14.6-inch front rotors, new four-piston fixed front calipers and some upgraded rear hardware are likewise supposed to reduce brake fade under suboptimal conditions while also improving pedal feel.
Similarly new for the segment is the “rack‑and‑pinion Electric Power Steering system.” General Motors claimed that the unit offers reduced kickback, which would be nice on particularly bad terrain. The system is also supposed to offer 30-percent more power than the current HD hydraulic steering gears designed for particularly heavy loads.
While I’ll happily criticize electric steering on typical passenger cars for robbing us of feedback, they offer clear advantages of off-road vehicles. HD pickups arguably don’t need a lot of steering feel to do their jobs and GM is claiming the new unit is even better than traditional hydraulic setup. It’s supposed to make the truck easier to steer while also being just as reliable thanks to “built-in system redundancy plus corrosion- and impact-resistant hardware designed for harsh heavy-duty truck environments, including rough terrain, road debris and severe-duty use.”
We’ll have to see how it all comes together when the 2027 Chevy Silverado HD and GMC Sierra HD launch later this year. But it seems like the manufacturer is trying to modernize its working trucks in a way that offers functional improvements while launching assurances about dependability. Considering the recent price increase of the non-HD pickups, we’re curious to see how much the manufacturer thinks that should cost.
While a base-trimmed 2026 Chevy Silverado 2500 (WT, regular cab, long bed, rear-wheel drive) can technically be found for $47,000, anyone buying one to use outside of a construction site will presumably be spending thousands more for a crew cab model. But the sky really is the limit on these kinds of trucks and anything from the 2027 model year equipped with the new 8.3-liter Duramax diesel will assuredly retail for at least $10,000 more than the equivalent HD gas burner.
[Images: General Motors]
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