Ford’s 6.7L Power Stroke is a great engine, and it’s the longest-running diesel V-8 to ever power the brand’s pickups, but the earliest version was equipped with a turbo that’s prone to failure. Despite its integrated wastegate (the mechanism used to bleed off excess drive pressure), the variable geometry GT32 SST aboard ’11-’14 engines is simply too restrictive in the Power Stroke application and often suffers damage due to overspeeding. Luckily, when Ford did away with the GT32 for the ’15 model year it did so without changing much else on the 6.7L Power Stroke. It didn’t take the aftermarket long to come up with a great solution for ’11-’14 Super Duty’s with failing or ailing turbochargers—they could be retrofitted with a late model (and much more reliable) turbo.
The best part of swapping a ’15-’19 turbocharger onto an ’11-’14 Power Stroke? It’s an OEM solution for an OEM problem, with nearly every part required to pull off the changeover being a genuine Ford component. This means not only is the fit and finish perfect, but the parts are generally readily available. In the diesel aftermarket—a segment that thoroughly celebrates the best-selling 6.7L Power Stroke in a multitude of ways—it’s a sound solution for a common problem. Below, we’ll show you what you need as well as explain why the ’15-’19 turbo is so much more reliable than the unit found on earlier engines.
GT32 SST
In many ways, the Garrett-produced GT32 SST is a modern marvel of turbocharger engineering. The SST acronym stands for single sequential turbocharger, which means the turbo makes use of two compressor wheels. Beyond that, the GT32 is of a variable geometry design, with movable vanes directing exhaust flow within the turbine housing to allow the turbo to perform like a smaller unit at low engine speed and a larger turbo at higher engine rpm. The GT32 is also equipped with an internal wastegate and a dual ceramic ball bearing center cartridge.
Dual Compressor Wheels
The GT32 SST’s dual compressor wheels both reside in a single compressor housing but sit back to back on the turbine shaft. The first compressor wheel receives air through a traditional opening in the compressor housing, while the second wheel gets its air via an upper inlet cast into the housing. Both compressor wheels feature 46mm diameter inducer measurements. By comparison, the 6.7L Cummins and the LML Duramax manufactured during the same era featured 60 and 61mm compressor wheels, respectively (although in these applications there is only one compressor wheel in play).
Failure Due To Overspeed
The fact that two compressor wheels hang on the end of the GT32 SST’s turbine shaft is likely the reason for the dual ceramic ball bearing center section. Well, in addition to the fact that the turbo’s shaft speeds are regularly over 100,000 rpm… In fact, with aggressive aftermarket tuning in the mix (which is very common on diesel trucks), turbine shaft speed can exceed 150,000 rpm—and this (as well as extremely high drive pressure) is the primary reason for this turbocharger’s overspeed failure rate.
Introduction Of The GT37 And Why It’s More Reliable
For the second-generation 6.7L Power Stroke, which debuted for ’15 model year Super Duty’s, Ford reverted back to a traditional turbo design, but one that could move more air and exhaust. The Garrett GT37 it elected to use makes use of a single 61mm compressor wheel (vs. 46mm on the GT32 SST) and a turbine wheel with a 72.5mm inducer (vs. 64mm on the GT32 SST). Larger wheels on both ends of the turbine shaft translates into more flow, lower shaft speed and ultimately less overspeed potential, which is why there is not a need for a wastegate on the GT37. Last but not least, the GT37 also utilizes a journal bearing center cartridge (cheaper to rebuild) as opposed to a ball bearing one in the GT32 SST.
The Fix: ’15-’19 Turbo Retrofit Kit
Despite all the differences between the GT37 and the GT32 SST, the GT37 is still a variable geometry turbocharger. This means you don’t sacrifice much performance (if any) in the way of low-end torque (i.e. responsiveness, pulling power and drivability), but you do get a much more reliable turbo. Using ’15-‘19 model year parts, many aftermarket companies offer comprehensive systems to convert your ’11-’14 6.7L Power Stroke to one based around the use of a GT37. Midwest Diesel & Auto, KC Turbos, No Limit Fabrication, RCD Performance, Snyder Performance Engineering and Ford Racing all sell everything you need to put your early 6.7L Ford on the road to reliability.
A Turbo Swap Using All OEM Parts
Using factory Ford parts intended for the ’15-’19 engine, the original 6.7L Power Stroke can be retrofitted with the more dependable GT37 Garrett VGT. The swap calls for the GT37 turbo itself, its mounting pedestal, ’15-’19 turbo up-pipes (shown), a ’15-’19 passenger side exhaust manifold (preferably with the accompanying OEM heat shield), a ’15-’19 two-piece, 4-inch diameter downpipe, updated oil and coolant feed lines, a ’15-’19 lower intake manifold or aftermarket replacement and all necessary gaskets, clamps and hardware.
Better Reliability, More Horsepower
Because the factory GT32 SST limits high-rpm airflow so much on the ’11-’14 Power Stroke, additional horsepower is immediately unleashed when a ’15-’19 GT37 replaces it. In aggressively tuned applications, 40 hp gains are regularly experienced. So not only do you get a more reliable VGT and very little sacrifice in low-end torque (if any), but you also pick up considerable horsepower in the process. With a GT37 VGT in the mix, the horsepower curve of the 6.7L Power Stroke extends beyond 3,000 rpm, whereas it peaks at 2,800 rpm with the restrictive GT32 in place.
Get Covered. Get Retrofitted.
With a GT37 turbo installed on a tuned ’11-’14 Super Duty, more than 500rwhp and 1,000 lb-ft of torque is on the table. That’s a pretty potent ride for minimal investment—but it also makes for an engine package that will last indefinitely. As the early 6.7L Power Strokes continue to age, most are aging well, but the ones that’ve been fitted with a GT37 are truly set for the long-haul.