6.0 with 6-speed / 4.10 gear rpm

Sirspeedy · June 23, 2016

Guys what is the average rpm the truck runs at 70 MPH with the 6.0 6-speed 4.10 rear?

Thanks for the help!

Skeld · June 23, 2016

About 2,000 RPM in 6th.

Cowpie · June 24, 2016

I have a spreadsheet put together that shows the road speed at various RPM's for the 6.0L 6L90 4.10 setup. One can even change the tire revolutions per mile and get road speeds across the board. Great for those who want to see what different tires do. Can't seem to upload an .xls file on the post. Send me a PM with your email if you want the spreadsheet and I will send it.

Here is a screen shot of the spreadsheet with stock tires showing various RPM's and road speeds. Very accurate. We use this kind of stuff for determining road speeds and RPM's using various diff ratios and tires on commercial semi trucks.

crankman · June 24, 2016

About 2,000 RPM in 6th.

Same here

Tjeli · June 24, 2016

Yep. Right around 2K or so. I would take 4.56s if they were available as a factory option.

-Eli

SMiller · June 25, 2016

Yep. Right around 2K or so. I would take 4.56s if they were available as a factory option.

-Eli

Sign me up as well! Having two tall worthless overdrives doesn't help when I don't have enough power to seeing them, might as well put the engine in the power and and get the gearing down to get me moving. Mileage would be the same and these motors last forever so win/win.

MotionMan · June 29, 2016

2000 and under is the sweet spot and gives the best MPG. I see 1900-2000 at 70. That gets me 16mpg hwy (that's on the avg meter on the dash, hills drop it a bit) but I average 14 after 5000 mikes, I think it will improve once it breaks in.

Cowpie · June 29, 2016

2000 does seem like where the motor has a nice balance of power and economy. It is also where the L96 6.0L hits 90% of available torque. On two lane rural highways in my area which are curvy and hilly, I generally keep the trans in manual mode and in 5th gear. A lot less gear searching, keeps the RPM's in the 2100 RPM range, etc. I just wish I could get a fuel map on the 6.0L like I can a HP and Torque map, but my suspicions is that it would show around 2000 RPM as the lowest GPH on the curve. That 1900 - 2100 RPM range really is sweet spot for the motor. I generally still run around 65 on the major highways, so I can pull off some pretty good mpg out of it. 17-18 on road trips.

Edited June 29, 2016 by Cowpie

Skeld · June 29, 2016

If we were going for pure fuel mileage I would think lower RPM would be better. I mean my 2009 1500 with the 5.3 would turn like 1600 or 1700 maybe at 70 in 6th? It was gutless but they are going for fuel mileage in the 1500's over pulling power.

Cowpie · June 30, 2016

On the surface, that would make sense regarding lower RPM equals better fuel economy. But there is rotational inertia in a engine that comes into play among other things. Too low of RPM, and the engine is fighting rotational inertia. It takes more fuel to get the job done. RPM is not what uses fuel, it is the amount of fuel needed to generate a specific level of power at a particular RPM. A engine coasting downhill at 4000 RPM is not using much more fuel than a engine coasting downhill at 2000 RPM. Also, too low of RPM, and with any kind of terrain change, and transmission is shifting more frequently, which is also a mpg killer. Too high of RPM also is a mpg killer. It can actually take more fuel to move a vehicle at 1500 RPM than it does to move it at 2000 RPM, simply because it takes more fuel to generate the same power needed to move the vehicle at 1500 RPM than at 2000 RPM.

On commercial engines, the OEM's provide not only HP and Torque mapping, but also fuel consumption mapping. The map as a U curve across the RPM range. At lower RPM's under load, fuel consumption per hour is higher, then drops as it approaches optimum "sweet spot" of the engine where it is lowest, then rises again as RPM's move higher out of the sweet spot on the engine. I wish we had that sort of information on our pickup engines. From my experience, it seems the best overall sweet spot for the 6.0L seems to be in the 1900-2200 RPM range. The is why I keep it in M5 on the rural highways with their lower speeds, and only run about 65 and no more than 70 on the major highways. Both situations, keeping the RPM's in that 1900-2200 range. 14 mpg lifetime average over 22K+ miles... frequent gravel roads, off road farm and ranch, in town, highway, everything. Also consistent 17-18 mpg on road trips.

Take all of this and then look at why that 1500 was gutless at 1600 RPM. It was clearly out of the engine sweet spot.

Edited June 30, 2016 by Cowpie

Skeld · June 30, 2016

Could be although as you can see it's a trend to keep gearing the 1500's higher and higher. Plus a lower numerical rear end usually equals better mileage. I see what you're saying but you can't argue with the mileage on the new 1500's being around 20ish possibly on the highway. In practice for me all driving it ends up being a much lower number but you get them out on the highway and do that only and you will see some pretty impressive numbers. It's hard to pinpoint what is most advantageous though compared to the 2500, we have a lot of factors. Direct injection, gearing, lower weight, lower ride height (aerodynamics).

Cowpie · June 30, 2016

That is true on the 1500 side, as the majority use is basic transportation. Whereas, the 2500/3500 side is majority commercial use. Those of us in commercial activity that need trucks, both large and small, take what I mentioned into account far more than the average 1500 user.

Angel Medina · March 18, 2022

On 6/24/2016 at 8:09 AM, Cowpie said:

I have a spreadsheet put together that shows the road speed at various RPM's for the 6.0L 6L90 4.10 setup. One can even change the tire revolutions per mile and get road speeds across the board. Great for those who want to see what different tires do. Can't seem to upload an .xls file on the post. Send me a PM with your email if you want the spreadsheet and I will send it.

Here is a screen shot of the spreadsheet with stock tires showing various RPM's and road speeds. Very accurate. We use this kind of stuff for determining road speeds and RPM's using various diff ratios and tires on commercial semi trucks.