Higher RPM's but less fuel...

[poptopjr]

With taller tires, I'm running 305/70's, would 4.10's actually help improve my fuel mileage?

I've always figured a taller gear meant higher RPM's which meant more fuel, but it should actually take less fuel to go the same speed, shouldn't it?

I'm still learning about the 6.5, I've read that 1800 RPM's is where the most torque is created and that is where the best mileage is.

What is the preference? I tow a boat, about 5k pounds, but a lot of drag. I'm thinking of switching to 4.10's from 3.73's. What should I expect?

Thanks for your input.

Keith

 

[NVW]

The 4.10's will increase your rpm's over the 3.73's. The number is the ratio of the drive shaft rotations to the axle shaft rotations.

With the big tires you have they may be hurting mileage.

 

[WarWagon]

Sweet spot on my truck is 2100-2200 RPM. This has the best torque with the 4l80E to maintain speed with my trailer. I expect the best fuel economy there at peak torque. Each truck is a little different.

Wider tires have more contact patch and more friction to suck fuel.

 

[ak diesel driver]

1800 is probaly the empty sweet spot. Loaded it is a little higher like WW stated

 

[buddy]

Depends on how fast youre going. 3.73s is a taller/higher gearing than 4.10 and will go the same speed at lower RPM than 4.10s. Lower RPMs is less fuel normally, and better economy. If you want higher RPM just put it in 3rd gear.

 

[poptopjr]

I don't really "want" higher RPM's, I was just questioning the peak torque/peak mileage theory. I won't change to 4.10's until other mods have been completed. I only tow about 5k pounds right now, and don't get me wrong, it goes down the road at 60 mph just fine. I just want it to go down the road better... but who doesn't?

 

[buddy]

3.73s are fine, you just need a PCM program update, and a few other mods,

 

[Turbine Doc]

As a FYI my latest re-flash & all goodies in my signature running 2400 rpm or 78 mph in cruise control I got 17 mpg with my 3:73s truck bed fully loaded with about 600-700# of "stuff" and another 400# me & stuff in the cab, I didn't run by the scales but I'm guessing the truck was in neighborhood of 7K +/-200# with all the extra weight on-board.