What Rear Gears do I want on a 13 speed

They run west coast mountains with them. I wouldn’t prefer it, but for mileage and power I’d go 3.36 or 3.33

 

Then swap out ur rear end neither 3.08 or 3.25.

 

The final ratio at the out put shaft for the 10 or 13 speed is the same .74. The 3.55 rears are an all around rear end. If your trying to lower your rpm at cruzing speeds then lower your ratio. I run 2.64 rears on lo pro 22.5 tires and have no trouble on the hill I also have 2050 FTLB of torque and 500HP.

You have to see what your engine is rated at. Meaning newer engines make torque a lot lower and are designed to run at lo RPM's. Some of the older cummins are not. At 60 MPH I am turining 1050 RPMs that is way too low for an older cummins.

 

13 speed is .73 to 1 on top gear.

 

You might be right but thought for sure it was .74

 

I have a Volvo D12 w/ 425HP mated to 10spd + 3.90 rear end.

She pulls up the hills on I-81 easy. Keeps up with all the big boys, and I never have to drop a gear to crest hills (though I never gross 80K -no need to).

My truck came equipped with Volvo Road Relay...and it's always telling me to upshift after I hit 67mph (Annoying, but Hey!). She's usually at 1650RPM on 65mph cruise.

If the tranny croaks, I swap it with a 13spd and maybe I'll get even better MPG. right now I'm averaging 7.8MPG on IFTA miles.

 

Also waiting that to happen to the blue t600. Swap to 13/18 speed for well fracking/otr operations.

 

The difference on .73 and .74 you won't ever feel from the seat, the tank or any where else.