[kos]

One of the trucks is a 2004 Freightliner 14l Detroit 435/500hp 3.42 ratio automatic 10 speed, the other one is a 2004 Freightliner 12.7l Detroit 430/470hp 3.58 ratio 10 speed. I would really appreciate any information on the fuel consumption of this 2 trucks if they are carrying the same weight on the same terrain.

[marylandkw]

In my humble opinion....

I would go for the first truck. That 3.42 would help keep your rpm's lower at highway speeds and the auto always makes the perfect gear choice, or at least it tries.

Both trucks are speced fairly well and would likely be pretty close on mileage. But just remember, Fuel mileage is most affected by the DRIVER. I have 4.11's and an 18 speed and get a consistent 7mpg.

[BanditsCousin]

The mileages and sleepers can play a role.

Automatic transmissions use more fuel in automobiles, thats a fact. Not sure about trucks.

[GMAN]

I think the gears may help you slightly with the automatic, but the straight shift will help you on the other one. I think they will be close on fuel mileage. If mileage is your goal, I would probably go with the straight shift.

[Gibby]

Well I do not know about the straight shift being more economical, my T600 w/ 550 cat, 18 spd auto shift,3.36 ratio gets nearly .7 mpg better than my partners truck that is equipped the same except his is manual 18.. remember the computer controls shift points allot more accurately than a human can. Both trucks have 86" studio, and both pull 53' 10'2" spread Merrit cattle pots.

[BanditsCousin]

My Dad's friend said the 10spd was the most efficent trans. I have no data or evidence to support that

[allan5oh]

What are the tire sizes of the two trucks? Also final gear ratio?

Without those, you can't figure out cruise RPMS.

[BanditsCousin]

They are 3.48 and 3.52 as stated above in his original post :wink:

I'm assuming both models are the same and hes comparing the two, but if one is a cabover and another a century class, we have some "variables" to explore here

[BanditsCousin]

They are 3.48 and 3.52 as stated above in his original post :wink:

I'm assuming both models are the same and hes comparing the two, but if one is a cabover and another a century class, we have some "variables" to explore here

[allan5oh]

I meant the final gear ratio of the TRANSMISSION.