Gear Ratio change for fuel savings.

I think Cummings has an online calculator to find what puts you in the right rpm range with what gear, trans and tire size. If not I'm sure fuller Easton does.

 

What are the savings in mpg you are looking for

 

A hard puller to the left or the right? Sorry Banker I had to do it lol. I didn't think there was any of their trucks that really pulled.

 

http://www.roadranger.com/ecm/groups/public/@pub/@eaton/@roadranger/documents/content/ct_062746.swf

You will also need the Horse Power & Torque curve chart for your Particular Engine to do It Properly

 

I had a 2006 Century with a 450 Mercedes. It originally had 3.58 rears on 11R22.5 . It was a real dog. I switched jobs and went from 5 axle 80,000 lbs to 8 axle 140,000 lbs super-b and changed the rear ratios to 4.11 at a cost of $5,000.
Later I went back to dry van and the truck picked up almost a full 1 mpg. I guess that Mercedes liked to spin faster then I was told. 1,500 rpm at 100 kph (62.5 mph). I could do 70 mph but it killed the fuel economy drastically. But it was still a bit of a dog.

 

I did leave myself open for that! It didn't run like my Pete, but it was a fresh rebuild and surprisingly it really did run and pull good. I felt like it ran better after I polished the wheels and tanks. Just kidding!! It was better than my Allied truck that ran 75 but laid down on a slight grade empty.

 

I really doubt you will ever see 8, we are at 8.5 with a setup that is 10,000 lighter, smaller motor, and a LOT less drag and rolling resistance, on only 3 axles. If I remember right the best we could do with that 7 car Pro star setup was around 5.5.

Remember, that even 5 car is going to be no where near as aero as a box van.

 

Are you running tall or short 24.5's?