rear axle gear ratio

25MPG, must be those British Imperial gallons. Chris

4x4ord wrote:
It's real hard to know when you're on a flat road . . .

Agree. I use a GPS that displays the elevation very accurately, realtime. Can't tell you how many times we thought we were going downhill when the GPS showed we were going distinctly uphill---and vice versa.

4x4ord wrote:

Cummins12V98 wrote:
^^^^^^^^^^^^^

Man you make my head spin! :B

I just know I can easily make my Dually get 20 mpg on flat ground at 55 but as soon as you have a small rise in the road that vanishes.

Realty is a trip at 60-70 freeway speeds with no winds and mildly varying elevations I can get 16 hand calc, THAT'S REALITY.

Cummins12V98 wrote:
^^^^^^^^^^^^^

Man you make my head spin! :B

I just know I can easily make my Dually get 20 mpg on flat ground at 55 but as soon as you have a small rise in the road that vanishes.

Realty is a trip at 60-70 freeway speeds with no winds and mildly varying elevations I can get 16 hand calc, THAT'S REALITY.

It's real hard to know when you're on a flat road with no wind. That's why I like calculating my fuel economy based on a round trip or at least knowing that the elevation is the same where I ended as where it was when I started. The road from our house into town has an elevation gain of 300 feet over a 7.5 mile distance. I can average about 13 mpg going into town and about 21 coming home.

I agree for sure! There is highway 99 south of Sacramento to Bakersfield, CA that going either way with no wing I get good mileage. I have to look at the foliage along the road to determine wind or no wind.

The trip I mentioned was to and from on a calm day. It was near sea level in the PalmSprings and South East area.

Cummins12V98 wrote:
^^^^^^^^^^^^^

Man you make my head spin! :B

I just know I can easily make my Dually get 20 mpg on flat ground at 55 but as soon as you have a small rise in the road that vanishes.

Realty is a trip at 60-70 freeway speeds with no winds and mildly varying elevations I can get 16 hand calc, THAT'S REALITY.

Cummins12V98 wrote:
^^^^^^^^^^^^^

Man you make my head spin! :B

I just know I can easily make my Dually get 20 mpg on flat ground at 55 but as soon as you have a small rise in the road that vanishes.

Realty is a trip at 60-70 freeway speeds with no winds and mildly varying elevations I can get 16 hand calc, THAT'S REALITY.

It's real hard to know when you're on a flat road with no wind. That's why I like calculating my fuel economy based on a round trip or at least knowing that the elevation is the same where I ended as where it was when I started. The road from our house into town has an elevation gain of 300 feet over a 7.5 mile distance. I can average about 13 mpg going into town and about 21 coming home.

^^^^^^^^^^^^^

Man you make my head spin! :B

I just know I can easily make my Dually get 20 mpg on flat ground at 55 but as soon as you have a small rise in the road that vanishes.

Realty is a trip at 60-70 freeway speeds with no winds and mildly varying elevations I can get 16 hand calc, THAT'S REALITY.

If the road is level and you can get 25 mpg there is no reason why you shouldn't be able to average 25 mpg on a long return highway trip. The only fuel economy number that has any value at all is one that is averaged over at least a tank of fuel and ends at the same spot it began.


If you are traveling up a 1% incline at a speed that requires 64 hp to maintain in an 8600 lb truck it will take 36 Hp to maintain that same speed going down.

goducks10 wrote:

gmc6000 wrote:

tinner12002 wrote:

4x4ord wrote:

tinner12002 wrote:
Go with 4.10s and don't fall for the hype of getting better fuel mileage with the 3.73 because you'll likely not see a difference. With the new trucks they are geared to nearly the same high gear for mileage. I'd also recommend getting the Aisin trans if they have it. Just my opinion.

What do you mean by stating "with the new trucks they are geared to nearly the same high gear for mileage"?

The difference between the 3.73 and the 4.10 trucks, and I'm referring to trucks in the last 3-4 years, I drove was as close as I could tell, 150rpm, not enough to make a significant difference in MPG even as calculated. 3.73s give up about 5-6K pounds of tow capacity also. You can tow with any ratio you want but in my opinion the 4.10s are the way to go. On a straight and level road at 55mph my truck empty will get 22-24mpg and have seen it as high as 25. Hand calculated vs comp was only .5 mpg off so I've checked both ways.

There is no way in hell you are getting 22-24 MPG with a dually truck, unless the straight and level is downhill all the way.

He's cruising the internet. It'll be less when he's out on the hwy.

Not cruising anything, I didn't say I was averaging 22-24mpg, I'm saying driving down a LEVEL hiway I seen 22-24 on the comp, even as high as 25, that's a calm day, 55mph and level roads with the truck in my sig. So yes way in a dually!

Suburban gasser 7.4L, 4.1's, oversized tires and not corrected in the computer

Should be just a hair under 2,000 RPMs cruising at ~65MPH (4L80E OD = 0.75) if corrected in the computer, or the actual speed would be over 70MPH


subdash suburbandash mysubdash

steve-n-vicki wrote:
I have 3.55 gears and at 65 mph I am turning just about 2600 rpm in 3rd gear (1 to 1 ratio) so I have a final drive ratio of 3.55 to 1

And 245/70R16 tires.

I have 3.55 gears and at 65 mph I am turning just about 2600 rpm in 3rd gear (1 to 1 ratio) so I have a final drive ratio of 3.55 to 1