What Rear Gears do I want on a 13 speed

I currently have a Cummings with an EF auto 10 and 3.55 rears and i love the combo. great pickup speed, good on hills, MPG could be a little better.
I'm looking at going to a EF auto 13 with a Cummings, what rears would give me the same out come and maybe a tad better MPG?
I run East coast, SC to MA and out as far as IA. loads from 30K to 45K regularly.

 

Some guys really take offense to misspellings .... It's CUMMINS , not Cummings ... Like calling a FORD a FERDE , obviously wrong.


CUMMINS has made a lot of motors, which one do you have?

Generally speaking, a 3.08 is completely feasible with where you run.

I run 2.64 rears with a overdrive 12spd trans in that lane running gross wt#


.

 

It's "a lot" not "allot", lol.

Sorry, couldn't resist.

 

Haha thank you!

 

I can't give any advice with an automatic, but as an old timer, there's nothing wrong with calling a "Columbus Vibrator" a Cummings.

 

Sorry guys - auto correct can be a pain when it corrects the wrong thing -

I have a ISX15 Prostar (Don't laugh she runs like a demon) with the EF Ultra 10. I'm looking at an EF UltraPlus 13. so to get basically the same pull up the hills, the same pickup and go (passing power) and hopefully a little better MPG, on the 13 speed what rears? i am assuming its not the same or is it?

 

What is the final ratios of the Trans? 11r tires or low pro? Where is the torque peak for that engine. Crunch those numbers and you should have your answer.

 

How doe this sound to anyone?
Pacar MX13 (currently set at 455hp) with a Ultrashift PLus 13, running 22.5 Low Pro and a 3.36 rear ?

 

Mx13, 13 speed, 22.5 lo pro with 3.36.
65 mph@1375 rpm and 70 mph@1475. Sweet spot for 455 hp 1650 torque is between 900-1400 rpm which the fastest you can set your cruise on is 67 mph.

 

You might even look for a lower rear end ratio if just running east coast and Midwest. I know christner runs like a 2.94 or 2.64 and they get great mileage