Nearly 20 years ago, General Motors was about to debut an innovative new engine that had the potential to change the landscape of pickup trucks. That launch never occurred.
The 4.5-liter turbodiesel V8, referred to as the Baby Duramax, was on the verge of production, even showcased in a Suburban as a concept at a SEMA show one year, and promised to upend conventional standards while setting new records in the half-ton truck market. Then the 2008 financial crisis struck, GM declared bankruptcy, and the Baby Duramax was put on hold. GM claimed that all prototypes were destroyed, yet at least one managed to escape their control and found its way to Sweden.
This isn’t an exaggeration. The Baby Duramax was set to offer more torque than any other engine available in a half-ton truck back then, provide superior fuel efficiency compared to competitors’ lower-powered engines, and included technology that wouldn’t be seen in sports cars for another decade. It was an engineering wonder that seems to have been simply too advanced for its time. What could have been, or rather, what could still be, as at least one prototype exists today. Are there more? How many? Where are they located?
On the latest edition of The Drivecast, we delve into the Baby Duramax, codenamed LMK, exploring its history, potential, and the prototype that made its way into the public domain.
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Complete Transcript
Caleb: All right, Joel. I’m thrilled to finally discuss this on a podcast. This topic consumed a substantial amount of my time as I researched the story regarding the lost Duramax. And, here we are, which is quite ironic considering you just spent the previous week with a Silverado EV Trail Boss. Quite a different beast, don’t you agree?
Joel: Absolutely. We’re living in a radically different era compared to 2008 and the LMK and all those circumstances. It’s true. I just had a Chevrolet Silverado EV Trail Boss, and, you know, it’s an electric truck, right? With a massive battery pack, heavy, boasting all the torque—775 pound-feet of torque—and the horsepower—725 horsepower. On 35s, off-roading, and so forth, it’s a walking contradiction. We’ll do a review on it. But it’s ironic how we’re discussing the Baby Duramax and what could have transpired, given that we’re in such a contrasting era. History would likely have been altered in the truck market, which we’re about to explore. Before we dive in, Caleb, can you walk us through what we’re talking about? The context, the events that unfolded, and the history leading up to the discovery of the engine that escaped destruction?
Caleb: Sure. So, the 4.5-liter Duramax was a project that gained momentum in the mid-2000s, toward the end of that decade. It was a unique initiative aimed at innovating the half-ton truck segment, which was quite competitive back then, with the Big Three—GM, Ram, and Ford. Reflecting on those days, the half-ton market wasn’t particularly commendable at that time; maybe that’s just my opinion. Ford had the 5.4-liter Triton—still subjected to negative opinions years later—and GM was strategizing ahead by considering, “Let’s develop a diesel engine for these 1500-series trucks.” This would truly take people by surprise. It would outperform the small-block gas V8s significantly. They focused on an engine that could fit wherever a small-block V8 would fit, achieving better fuel efficiency and also producing 520 pound-feet of torque. They succeeded in that mission, investing hard work to bring it to reality. It incorporated a hot-V turbocharger, which, if you’re familiar with high-performance sports cars, you know was featured in the Mercedes-AMG GT and the Cadillac CT6-V Blackwing, which are exceptionally rare. GM effectively brought this technology into the Duramax diesel around 10 years prior. This was a remarkable engineering achievement, not just for its time—2006, 2007—but it would still be regarded as special today. That torque figure remains unmatched by contemporary light-duty diesel engines. It was on the verge of greatness, but as the years 2008 and 2009 approached, GM’s Chapter 11 bankruptcy put an end to it. What remained were only tales about this engine; there were no firsthand accounts of anyone saying, “I reviewed this engine, and it performed this way.” I gained some insights by interviewing individuals who witnessed it firsthand, including Gail Banks, who is quite notable.
Joel: Before we delve deeper into the specifics of the engine, I just want to clarify a few things Caleb mentioned to highlight the scope here. It’s not just about the trucks, right? You emphasized a key point there, Caleb—that this engine could seamlessly drop into any vehicle designed for Chevy’s small-block V8. That means it could have fit into an Escalade, a Tahoe, a Suburban, or a Yukon. It would have opened the doors to an entirely different era compared to what we experience today or, interestingly, we’re somewhat living in it now but two decades back. There was nothing like this on the market — no small, compact V8 turbodiesel or any other turbodiesels in those trucks or SUVs. Also, regarding the hot-V configuration, which is presently associated with high-performance sports cars, we see it in M5s, AMGs, and Audis. Yet, these are all high-end sports vehicles, and not pickup trucks. Moreover, the duty cycle and usage of a pickup differ vastly from that of a sports car. Sports cars are designed for high-speed track use with ample airflow cooling their systems. Whereas in a pickup, you’re not cruising at 150 or 125 mph on a race track; you’re traversing a steep grade, hauling something, at lower RPMs. It’s a completely different use case, requiring lower RPMs, making the idea of integrating turbos into the V configuration astonishing for pickups two decades ago.
Caleb: Indeed. And what I often observe is that while I write extensively about four-wheel drives and body-on-frame vehicles, many dismiss them as overly simplistic. In reality, manufacturers often assign their brightest engineering minds to these truck projects for the very reasons you mentioned. Whether people truly use them as intended is another question. They are designed to perform in demanding conditions; hence, manufacturers test in locations like Colorado and various deserts. These trucks must endure hard work wherever they go. That’s why so many skilled engineers were involved in the LMK project. Earlier, I mentioned Gail Banks—who is recognized as a turbo diesel expert. He has been tuning these engines for longer than I’ve been alive, which speaks to his expertise, not a critique. GM invited him for a close look, exploring the possibility of selling them to marine clients for use in boats. In our discussions, he brought out handwritten notes from 20 years ago, and hearing his personal anecdotes from that era was one of the most fascinating experiences in my career. I find this topic truly enjoyable, and for anyone interested in trucks and history, I hope it resonates with them too.
Joel: Yes, and I want to touch upon the engine briefly before we proceed. You mentioned Gail Banks and his connection to the marine sector, which is interesting because the marine industry frequently utilizes modified car engines for inboard systems. For instance, my 1995 deck boat operates on a 5.7-liter Mercury, essentially a water-cooled Chevy small-block. Hence, the implications of this engine went beyond the automotive space, affecting marine and other sectors too. But I would rather focus on the truck engine now. GM stated all prototypes were destroyed after the program was terminated. However, like urban legends in the automotive realm, we hear outrageous rumors frequently, some with a grain of truth and others are just fabricated. It’s like folklore—what should we truly believe? However, it appears one engine did escape the hands of GM, and it’s in your possession! Not only did you discover it, but you also published photos of its existence and the story behind it. Share with us the details of this engine and how it all transpired.
Caleb: Certainly. As you mentioned, we discovered it, but in many ways, it found me. After I published articles about the LMK Duramax, presenting it as almost a lost tale, I later stumbled upon a post on Facebook Marketplace where someone claimed to possess prototypes of the engine. I was intrigued and reached out, engaging in a lengthy conversation. I introduced myself as a reporter eager to write about the find, but then all our conversation history vanished—every message and photo disappeared. I found that odd. Subsequently, I wrote a follow-up piece explaining how we initially identified these prototypes only for them to vanish. Not long afterward, a guy from Sweden, my new acquaintance Henrik, contacted me claiming, “I have one.” The fact that he reached out from across the ocean, stating he had one of these engines, was astonishing. I never anticipated that at all. We ended up discussing on the phone, and a tip: if you’re calling internationally, do it over Wi-Fi; it was a $63 phone call—but worth it.
Joel: There’s something called WhatsApp, my friend.
Caleb: Yes, learned that the hard way. But it was worth it, and I got it expensed, so it wasn’t a hit to my wallet. We developed a great rapport, and Henrik shared photos. He bought it as part of a bundle deal, initially looking for a turbo—he noticed this unique hot-V engine while exploring a lot. He thought, “This doesn’t resemble any of the Mercedes engines I’m accustomed to.” He purchased it and has held onto it ever since; it’s been a few years. I recently reached out to him, and he still has the engine on offer. So if anyone listening is interested in potentially purchasing it, I could connect you with Henrik. Though it might end up being just a decorative piece, it represents a significant piece of truck history.
Joel: That would have been an exciting project.
Caleb: It would have been. It would have posed challenges, considering it’s a late-2000s diesel with emission systems that became more stringent, including EGR and DPF components. So challenges aside, as of now, it’s June 2026, and Henrik still possesses the engine, and I have his email and phone number—just shoot him an email.
Joel: So, this entire situation is deeply ironic, right? We’re now in a time where Ram first introduced a turbo diesel 3.0-liter in their EcoDiesel for the Ram 1500, followed by Ford with a turbodiesel (also derived from Range Rover), and then GM introduced a 3.0-liter inline-six, by the way, rather than a V8. Ram has since discontinued theirs, and Ford quickly dismissed theirs as well—only lasted two model years. But GM retains theirs, still available in the Yukon, Suburban, and Tahoe. Although briefly included in the Escalade, it didn’t sell well, leading to quite a discussion around consumer choices. And GM now stands as the last option at the party, without offering a V8—though it is branded as a Duramax. Notably, it’s an inline-six. Everyone else opted for a V6, which adds another layer of irony. Why didn’t they just revive this engine, refresh emissions standards, and roll it out, Caleb?
Caleb: I believe it was primarily a matter of letting the past be. They wanted to develop something new. While there are advantages to inline-sixes over V8s, opinions on preferences vary between buyers of Cummins or Duramax or Power Stroke engines. The new Duramax inline-six is designed for pairing with a 10-speed transmission; I’m not sure what would have been paired with the 4.5-liter Duramaxes—possibly a six-speed. So, perhaps that influenced their decision. I can’t say for sure. While I lack exact fuel economy data for the 4.5-liter Duramax, matching the 3.0-liter inline-six’s efficiency would have been challenging. The smaller displacement runs smoothly and benefits from varied ratios via the 10-speed transmission. Ultimately, I think they aimed for improved efficiency and torque over gas engines, leading them to pursue a fresh design.
Joel: You make a fair point. The turbo-six can achieve impressive EPA ratings in the upper 20s, and we’ve seen real-world tests yielding nearly 30 miles per gallon in full-size pickups without heavy trailers. While the 4.5-liter V8 turbo diesel wouldn’t have achieved that, it would have delivered additional power, making the choice compelling. The smoothness of an inline-six adds to the appeal compared to V8s. That’s a scientific fact. Moreover, the previously available V6 turbodiesel in the Ford F-150, marketed as a Power Stroke and based on a Range Rover engine, was among the quickest spooling factory turbodiesels until the new Super Duty high-output versions showed up. Yet, it lacked the fuel economy, averaging around 24 to 25 highway miles per gallon. So,
Caleb: Correct, and you’re one of the rare individuals who’ve driven one of those Power Stroke F-150s. Personally, I’ve never encountered one in the truck-heavy Missouri Ozarks. The last time I saw one go by was ages ago. However, I do frequently see EcoDiesel Rams; they were bought up by many who likely weren’t aware that it was actually an Italian engine.
Joel: I won’t admit to having driven a Power Stroke F-150 on a trip to Duluth, Minnesota for the Ram 1500 EcoDiesel launch. If that did occur, you can imagine the expressions on the faces of the Ram PR team when I pulled up. They looked puzzled, which was amusing. I didn’t explicitly compare the two during the first drive, but I guarantee you I was the sole journalist capable of doing so, simply due to my proximity to the launch’s location. So, Caleb, with the current scene, does a diesel engine still hold relevance in a half-ton truck? There’s only one left.
Caleb: Absolutely, I think it does. Though high diesel prices can complicate that narrative for many, especially from the perspective of a 7.3-liter Power Stroke owner. Diesel’s current price is quite high, but the usability of diesel engines certainly remains relevant. The smoothness especially fits well in daily-use trucks like the Escalade. Many people utilize their trucks daily, translating to considerable benefits in fuel efficiency. The new 3.0-liter Duramax boasts 495 pound-feet of torque, which remains slightly below the LMK’s 520 pound-feet. However, 495 is still substantial, with the ability to tow upwards of 13,300 pounds. While the price of diesel is a concern, even if it is higher in some areas, it’s still a valuable option depending on conditions. The 3.0-liter Duramax has encountered fewer issues than some others, and I can’t see any reasons to shy away from it. Modern diesel trucks have evolved substantially.
Joel: We perhaps shouldn’t approach this with pure rationality. I certainly don’t. Final thoughts from you, Caleb, on the historical implications of what could have been.
Caleb: If this engine had launched successfully and made waves, you’d have seen competing manufacturers scrambling to respond. They’re well-aware of history now and can claim it just wasn’t the right period, but if GM had successfully introduced this engine, the landscape would have been radically different. What was in competition with it at that time? The 5.4 Triton and an outdated Hemi? Its launch would have been momentous. I’m uncertain about the outcome versus today, yet we currently see impressive engine options, including the new Duramax inline-six, which offers strong performance. You don’t even have to opt for a Raptor to experience exceptional torque in a regular EcoBoost F-150. Additionally, the Ram 1500 with the high-output Hurricane engine can leave quite an impression.
Joel: What a powerhouse!
Caleb: Many aren’t eager to acknowledge this, and while some folks still insist, “You have to stick with the Hemi,” time will tell about reliability. I can’t provide insights on long-term ownership of a high-output Hurricane either, but I assure you it feels like a premium $80,000 truck when it operates that quietly and accelerates swiftly. While it’s hard to speculate on what could have happened, it’s likely we’d have seen competitors launching diesel options of their own. However, regulatory changes always impacted the decisions of manufacturers, often more than people realize. Those regulations certainly affected the lull in diesel adoption post-launch, as companies needed additional time to comply with stricter emissions regulations.
Joel: I should wrap this up by sharing that, back in 2020 or 2021, Ford produced a limited F-150 that featured a narrow body with a high-output EcoBoost 3.5 twin-turbo setup—450 horsepower and 510 pound-feet of torque. This was far ahead of the Hurricane’s emergence from Stellantis, and when I towed our 5,000-pound boat, I felt like I was flying on the highway. I stomped on the pedal, and it lunged forward as if the boat wasn’t even there. It was incredibly fast for that time. Sadly, it was a short-lived option, and I’ve seen its used variants hold their value, which isn’t surprising. Those were impressive trucks.
Caleb: If you spotted an F-150 Limited rolling by, you were certain, “This person knows what they’re doing.” Either that or they were upsold.
Joel: Either or. But if anyone listening has more information regarding the Duramax, Baby Duramax 4.5 LMK engines or additional context about their existence, please reach out to us at [email protected]. We are eager to gather more insight on engines that managed to evade factory destruction as well.
Caleb: On that note, I’ll issue a personal challenge: they unveiled this 4.5-liter Duramax in a concept Suburban Z71. If by chance you possess artifacts or knowledge about its whereabouts, that would be amazing. Additionally, I must mention that Bob Lutz once placed one of these engines in a Buick Rainier! If you know the fate of that Buick Rainier or saw it firsthand at dealerships, please connect with me! Reach out at [email protected] or [email protected]—I want to continue this story. The conclusion does not have to be reached. Also, if anyone is interested in purchasing this engine, contact me. This may be an unsolicited request, but I want to see an outcome here.
Joel: Aside from Caleb promoting an engine from Sweden, it’s evident he’s losing sleep over the thought of a Rainier with a baby Duramax. If you can provide insights into these vehicles’ current whereabouts, feel free to reach out. We’ll end it here. Thank you for your time.