When it comes to the heavy-duty pickup segment, engine output is a major sticking point. Not only does engine output play a dominant factor in towing and hauling capabilities, but it’s also something of a bragging right for some owners. To this end, General Motors equips the Chevy Silverado HD and GMC Sierra HD with the 6.6L V8 L5P turbodiesel Duramax, boasting some impressive specs along the way. However, the competition in this segment is fierce, with Ford’s 6.7L Power Stroke V8 and Ram’s 6.7L Cummins I6 presenting formidable alternatives. Now, we’re comparing the spec sheets to see how the Duramax stacks up.
6.6L L5P V8 turbodiesel Duramax
The Duramax V8 L5P has a displacement of 6.6 liters, which is slightly smaller than the 6.7L engines offered by Ford and Ram. Despite this, the L5P delivers 470 horsepower at 2,800 rpm, making it competitive, but not class-leading in terms of power. Ford’s Power Stroke V8, for instance, outputs 475 horsepower, while the high-output version of the Power Stroke leads this comparison with 500 horsepower. On the other hand, Ram’s high-output Cummins provides the lowest peak horsepower of the three with 430 horsepower at 2,800 rpm.
While power is good, torque is better. As such, GM’s turbodiesel L5P generates 975 pound-feet at 1,600 rpm, which is impressive, but falls short of its rivals. Ford’s standard Power Stroke V8 delivers 1,050 pound-feet, while the high-output variant dominates with a massive 1,200 pound-feet of torque at 1,600 rpm. Ram’s Cummins also surpasses the Duramax in this metric, offering 1,075 pound-feet at 1,800 rpm.
To note, GM introduced upgraded output figures for the turbodiesel V8 L5P in conjunction with the 2024 model year, boosting it from previous ratings of 445 horsepower and 910 pound-feet of torque. While the improvements narrowed the gap, the L5P still trails Ford and Ram in raw torque numbers.
Check out the table below for a side-by-side comparison of the numbers:
| GM Duramax V8 | Ford Power Stroke V8 | Ford H.O. Power Stroke V8 | Ram H.O. Cummins I6 | |
|---|---|---|---|---|
| Vehicles | Silverado HD, Sierra HD | F-Series Super Duty | F-Series Super Duty | Ram HD |
| Engine Type | V8 | V8 | V8 | I6 |
| Displacement | 6.6L | 6.7L | 6.7L | 6.7L |
| Aspiration | Turbocharged | Turbocharged | Turbocharged | Turbocharged |
| Fuel Type | Diesel | Diesel | Diesel | Diesel |
| Horsepower (hp @ rpm) | 470 @ 2,800 | 475 @ 2,600 | 500 @ 2,600 | 430 @ 2,800 |
| Torque (lb-ft @ rpm) | 975 @ 1,600 | 1,050 @ 1,600 | 1,200 @ 1,600 | 1,075 @ 1,800 |
Comments
The Cummins is simpler in theory to fix due to its design, and does not require cab off repairs like PS (or maybe the newer Duramaxes do). However, I still see cab off repairs for Cummins, and somethings are harder to do on a Cummins than a Duramax, and vice versa.
They all have records for high mileages, so that says something.
Its all about the tuning ! And longevity of the internals ! I was a fleet mechanic for 32 years and i havent seen a ford SD that wasnt detuned by ford ever ! 6.0 – 6.4 or 6.7 ! They do this mostly on the first recall campaign no matter what the recall is for !
Duramax all day for 2 reasons. 1, they have less reported repairs than both Ram and Fod. 2, what’s the point of big engine numbers when they can’t be used???? For reference, the Power stroke can’t use full torque till 4th gear. Rams new engine can’t lock the converter till 2nd. The Allison can use full torque and lock the converter in 1st, putting more real power to the wheels. True, the HO power stroke can dropp 500 HP while on the highway, but acceleration on a ramp, where we actually care about the power, the Duramax has it beat. Only thing I’d like to see is steel pistons like in the LZ0. That would increase fuel efficiency.
I do agree with regards to Ford….but the Cummins has an impressive track record aside from few weaknesses:
1. VP44 or Dowel Pin issues in the 5.9s
2. Hydraulic lifter issues in the 6.7s now.
Ford SDs are good, but the engine ITSELF IS A NIGHTMARE to look at….yes, so is the Dmax nowadays, but the 6.7 PS I hear is more expensive for everything…….
I hear the TFL men saying that Cummins should be easier to service because you can service the engine at big rig truck service stops. Is that true?
I would like to focus on the fuel pumps of each truck..GM did right by getting those Bosch CP4 units out of them, when the L5P come out in 2017. Ram and Ford went to those Bosch fuel pumps. Nothing but problems for both of them. Ram had stop-sale for a while. And Ford is now telling customers, they are not going to replace the pumps just reprogram the software for them. Can’t move a Diesel if your fuel pump is a turd.
Installed banks cai,and derringer,
Woke l5p up. 500 to rw 1095 torque. The whole truck is better
With Duramax internals capable stock with few upgrades 800hp+ and still outlast either according to gail bankshe sold me onmy l5p…