The 3.0L Duramax is a wildly capable inline 6-cylinder diesel engine designed for full-size half-ton pickup trucks and SUVs. Due to its amazing power-to-weight ratio and towing performance, GM has chosen to offer this engine in everything from the Chevy Silverado 1500 to the Chevy Suburban and even the Cadillac Escalade.
The new 3.0L Duramax shares very little in common with its predecessor, the 4-cylinder 2.8L Duramax. It's been completely redesigned from the ground up and features many improvements, including a forged crankshaft, forged steel connecting rods, and a much stronger block design. The result is an engine that produces 277 hp and 460 ft-lbs of torque. of torque. This is comparable in torque to the more expensive 6.2L gas engine offered in most of the same vehicles.
In our testing, we noticed that the platform provided plenty of torque for pulling hefty loads along with a healthy amount of power for getting around town and passing on the highway. However, when it came to stepping on the pedal, the desired response left much to be desired. The overwhelming amount of dead pedal made this truck's performance feel a bit lackluster. We also found ourselves wishing it had more low-end power to help the truck feel a bit lighter and nimbler when taking off, especially when towing.
Where this engine really shines is in the amazing fuel economy it offers. With 22 mpg city and 26 mpg highway, this truck will get you far on a single tank. The unmatched fuel economy is made possible in part by the all-new 10-Speed transmission paired with the 3.0L Duramax. This transmission offers more gears and uses the same advanced controller as its big brother, the 6.6L, to keep the LM2/LZ0 within the optimal RMP range for the best possible fuel economy. Another area where the 10-Speed shines is towing. In our tow testing, this truck outperformed a tuned 2.8L before any tuning was installed on the 3.0L. Considering the similarity in HP, we attributed this mainly to the new 10-Speed Allison's superior gearing.
However, when it comes to unloaded daily drivability, the 10-speed can fall a bit short. In our experience, we found the transmission's constant, slightly drawn-out shifting led to an overall lack of power reaching the wheels. With the transmission constantly shifting, it also felt like the turbo never really had a chance to get into boost before the transmission shifts, de-fuels, and puts the engine at an even lower RPM. In this aspect, the 10-speed is a major buzz kill when it comes to having fun behind the wheel of your 3.0L.
With features like a forged crankshaft and a robust block design, we knew the 3.0L platform could handle additional power—and that custom ECM and TCM tuning was the perfect place to start. Our goal was simple: unlock the best possible performance from the stock 3.0L while maintaining the safety, reliability, and drivability owners expect. Achieving that balance wasn’t easy. To deliver on our vision, we went beyond basic calibration by developing both ECM and TCM tuning to correct the undesirable characteristics of the 10-speed transmission, while also offering multiple power levels designed specifically for safe, confident towing.
For our first round of tuning, we wanted to add as much power as we could while staying within the safe range the drivetrain can handle. To determine a safe power level for the 3.0L Duramax, we ran the truck on our dyno and monitored drive pressure, EGTs, and transmission temp to see how the engine, turbo, and transmission responded to the added power throughout the tuning process. After a few revisions, it looked like anything over 300hp was starting to negatively impact transmission temps and EGTs. However, the addition of around +40hp proved enough to deliver noticeable improvements in power, performance, and daily drivability.
For our second round of tuning, we wanted to create a tune we knew would be safe for your truck even with a full load behind it. Considering our towing experience went very well with the stock tuning. We knew that improving the torque curve and adding just a bit more power could make a great experience even better. The second tune we developed provides 25 additional horsepower and 60ft/lbs of additional torque. This was enough to provide a noticeable difference when getting heavy loads moving from a stop and passing on the highway with weight behind the truck. It also made the load's weight a bit less noticeable overall, while keeping drive pressure, EGTs, and transmission temp within safe ranges.
The factory torque curve for this engine is solid, extending well past 4000 RPM. With ECM tuning, we were able to increase the torque level across that entire curve. However, the transmission was still shifting before the turbo could really get into boost. Making It hard to get that additional power to the wheels. This is why TCM tuning was considered a must when approaching the 3.0L platform. The stock shift points simply don't allow the engine to rev out to its peak power even with ECM tuning. With our knowledge from tuning the 10-Speed Allison found in the 2020+ L5P, we set out to create a better TCM tune for the LM2 as well.
By adjusting the shift points and timing so the truck could reach higher RPMs before shifting, we not only massively improved the drivability and feel of the shifts, but also increased the amount of power reaching the wheels during 0-60 acceleration. This also reduced the feeling of the transmission constantly shifting and finally allowed the truck to reach closer to its peak power output before making the next shift. Along with adjusting the shift points, the de-fuel time between shifts was also adjusted. This not only helped mitigate the constant shifting problem. It also kept the power to the wheels running longer. This means higher average horsepower is delivered to the wheels when going through the gears after TCM tuning. The graph above shows how our TCM tuning on a 10-speed L5P decreased de-fuel times and can increase the average HP. Stock tuning is represented by the green line, and "with TCM tuning installed" by the red line.
With an added 40 hp and 100 ft-lbs of torque from custom tuning, plus our massive improvements in drivability and power output from TCM tuning, we finally felt like we had the truck's drivability where we wanted it. The added power finally made the truck feel lighter when accelerating and gave us more confidence while passing on the highway, especially when in tow tune with a load behind us. The truck also felt much more responsive with the additional power and improved throttle mapping. We were even able to observe a great improvement in MPGs during the course of testing both sport and tow tunes. Netting us an additional two miles per gallon on the highway in the sport tune with cruise control on.
After all was said and done, we were most excited that the truck now felt a lot more like its bigger brother, the 6.6L L5P found in the 2500HD. Plus we now had a truck that was legitimately fun to drive both loaded and unloaded. If you would like to learn more about custom tuning for your 3.0L Duramax, check out the product on Calibrated Power's website below.
