6.7 Cummins vs 6.6 Duramax

Simple, pop the hood on each. Class dismissed.

The Duramax is an Isuzu designed motor with the Allison transmission; I believe 2019 is gonna be the last year one can get a TRUE Allison 6 speed; they’re going to a Allison “branded” 10 speed for 2020....Hard to go wrong with the Duramax Allison combination.... Cummins motor is on par with the Duramax, but, not sure about the attached transmission.... I don’t think you will be disappointed with either....

Longer stroke engines have higher piston speeds.

azdryheat wrote:
My Duramax is quicker off the line than my friends Cummins.

My wife's Honda Civic is quicker off the line than my Powerstroke but I don't think I have ever pushed the skinny pedal all the way down without a trailer on behind and a big hill up ahead.

Thank you to all who have commented as these are exactly the sorts of things I was hoping to hear for but feared it would quickly turn into a fanboy debate. What a great community!!!!

azdryheat wrote:
My Duramax is quicker off the line than my friends Cummins.

This^. Have t been in a new Aisin HO Ram, but the LML and L5P will blow the doors off a 4th gen cummins/68 combo in a drag race.
I liken it to peppy vs thick power. But both will provide massive torque. Short stroke motor just spins up quicker.

IMO pick whichever one you like from a looks and ergos stance. But even that is pretty close. Both are quiet, powerful and comfortable IMO.

Both will still have a 6 speed auto for 2019. I'm excited about more trans gears in the future, but you're already future proofing your needs with that big of a truck.
I'd take an Alli trans over a 68 for mannerisms. But the 68 is proven just as reliable IMO and the 68 programming is vastly improved from Jist a few years ago.

Just a few things that I think about comparing the 2 trucks.

ib516 wrote:
In anything newer than about 2013/2014 its a chocolate vs vanilla argument. They're both great, but some like one better than another.

This! I'd take a new Dirtymax for its hotrod traits or a Cummjns for its simplicity. But I wouldn't think twice about getting either one with respect to reliability and power. Both are stellar IMO.

SidecarFlip wrote:
I like them all so long as they smoke....

I'll drink to that! Roll coal brotha!

Our 2009 Duramax has been flawless. Number 8 glowplug is the only engine issue we've had. Had to replace upper and lower control arms, tie rods and shocks. 167000 miles and going strong, hopefully another 10 years with him.

Since I'm not racing trucks I will stick with my Cummins diesel. There's lots of them rolling across the USA every day with over a million miles on the engine.