A 3rd gen turbo swap 6.7 cummins is one of those modifications that completely changes how your truck feels on the road, and it's usually the first thing people look into once their factory VGT starts acting up. If you've spent any time at all around the 6.7L platform, you know the drill: the stock variable geometry turbo (VGT) is a cool piece of tech, but it's also a notorious headache. Between the sliding nozzles getting stuck with soot and the constant threat of a massive repair bill, many owners decide they're better off ditching the complexity for something simpler and more reliable.
But what exactly are we talking about here? When people say "3rd gen swap," they're talking about taking the exhaust manifold and turbo style found on the older 2003–2007 5.9L Cummins (the 3rd Gen trucks) and adapting them to the newer 6.7L engine. It sounds a bit backward to use "older" tech on a newer engine, but in the diesel world, sometimes simpler is just better.
Why People Ditch the VGT
The stock HE351VE turbo on a 6.7 Cummins is designed to do a lot of things at once. It helps with emissions, it spools up incredibly fast, and it acts as an exhaust brake. That's all great until it isn't. The problem is that diesel engines are inherently dirty, and all that soot eventually gums up the moving parts inside the VGT. When those internal vanes get stuck, you lose your boost control, your exhaust brake stops working, and you might even find yourself in limp mode.
Beyond the reliability issues, there's the matter of backpressure. The stock VGT is quite restrictive. It's designed to keep heat in the engine for the emissions system, which is the exact opposite of what you want for high-performance or longevity. By performing a 3rd gen turbo swap 6.7 cummins, you're opening up the lungs of the engine. You're letting that 6.7L displacement actually breathe, which drops your exhaust gas temperatures (EGTs) and reduces the strain on your head gasket.
The Sound and the Feel
Let's be honest for a second—one of the biggest reasons guys do this swap is the sound. There is absolutely nothing like the sound of a fixed-geometry turbo on a 6.7L Cummins. Because the 6.7 has more displacement than the old 5.9, it moves a lot of air. When you pair that with a T3 or T4 manifold and a nice BorgWarner S300 or S400 frame turbo, the exhaust note becomes deep, throaty, and crisp.
You lose that "hairdryer" hiss that the VGT makes and replace it with a genuine roar. And the whistle? If you pick a turbo like an S366 or S369, the whistle is loud enough to turn heads three blocks away. It makes the truck feel like a proper hot rod rather than a restricted work truck.
On the road, the "feel" changes too. A VGT is very punchy right off the line, whereas a fixed-geometry turbo has a more linear power curve. You might notice a tiny bit more lag if you go with a huge turbo, but with modern wheel technology, these things spool up way faster than they used to. Once the boost hits, it hits hard and stays consistent all the way through the RPM range.
What Parts Do You Actually Need?
You can't just buy a turbo and bolt it on. A 3rd gen turbo swap 6.7 cummins requires a whole kit of parts because the factory setup is so different.
The Manifold
The heart of the swap is the exhaust manifold. On a 3rd gen 5.9, the turbo sits in the middle of the manifold, pointing down. On a 6.7, the factory turbo sits toward the back and points up. Most swap kits come with a high-flow cast manifold that centers the turbo. You'll have to choose between a T3 and a T4 flange. T3 is great for quick spooling and street trucks, while T4 is the go-to for big power and lower backpressure at high RPMs.
The Turbo Itself
This is where you get to have some fun. Most people opt for a BorgWarner S300 series turbo. An S363 (63mm inducer) is a fantastic choice for a daily driver that still tows. If you want more power and aren't as worried about towing heavy, an S366 or even an S369 can make some serious numbers. Some guys even go with an S400 frame if they're chasing 700+ horsepower, but that usually requires more supporting mods like injectors and dual fuel pumps.
Lines and Plumbing
You're going to need a new oil feed line and a new oil drain line. The factory ones won't reach or won't fit the new turbo's housing. You'll also need a new downpipe because the outlet on a 3rd gen style turbo is in a completely different spot than the factory VGT. Don't forget the hot-side intercooler pipe and a new intake setup—the factory plastic stuff won't work here.
The Exhaust Brake Trade-off
If there's one "downside" to a 3rd gen turbo swap 6.7 cummins, it's the loss of the factory exhaust brake. Since the exhaust braking function is built into the VGT's sliding vanes, once you remove that turbo, you lose the brake. For guys who live in flat areas or don't tow heavy, this isn't a big deal.
However, if you're hauling a 15,000-pound camper through the mountains, you're going to miss that braking power. The good news is that you can always add an aftermarket inline exhaust brake (like a Pacbrake) down the line. It adds to the cost of the project, but it gives you that peace of mind back when you're descending a steep grade.
Tuning Is Not Optional
You can't just swap the hardware and expect the truck to run right. The truck's computer (the ECM) is constantly looking for that VGT actuator. If it doesn't find it, the truck is going to throw a fit, light up the dash like a Christmas tree, and probably go into limp mode.
You'll need custom tuning—usually through EFI Live or EZ LYNK—to tell the computer that the VGT is gone. Good tuning is what makes or breaks a 3rd gen turbo swap 6.7 cummins. A talented tuner can adjust your fuel mapping to help the new turbo spool up faster and ensure your transmission shifts correctly with the new power curve. Without proper tuning, you'll end up with a smoky, laggy mess that's no fun to drive.
Reliability and Long-Term Value
At the end of the day, most people do this swap because they want a truck they can depend on. The VGT is a wear item; it's not a matter of if it fails, but when. By switching to a fixed-geometry setup, you're moving to a platform that has been proven for decades. There are fewer moving parts to break and less heat being trapped in the manifold.
While the initial investment for a full 3rd gen turbo swap 6.7 cummins kit can be a bit steep, it often pays for itself. When you consider that a new OEM VGT can cost a couple of thousand dollars just for the part, spending a little more to "fix it forever" with a 3rd gen swap makes a lot of sense. You get better reliability, better sound, and a truck that's significantly more fun to drive.
It's not necessarily the right move for every single owner—especially those who need to stay strictly emissions-compliant or those who absolutely rely on the factory exhaust brake—but for everyone else, it's arguably the single best upgrade you can perform on a 6.7 Cummins. It turns a complicated, choked-down engine into the heavy-duty beast it was always meant to be.