Calling all EcoDiesel drivers with 3.92 gears

[jeepin7]

This topic may be on here somewhere, but all I can find are conversations with Hemi set ups. I have a 23 Limited Night EcoDiesel with 3.92 gears. Picked it up used with oversized Nitto Ridge Grapplers, so never saw how it handled with stock P-metric 22in tires. I have corrected the tire size setting so the speedo is accurate and it made a difference with shift pattern and handling.

What tire combo are you running and where do you land RPM wise at highway speed?

I want to go to 285/55r22 to get the RPMs closer to the correct range, (1600-1900, 60-75mph) but this is a big jump from 33 to 34.4in tires to move the needle.
I calculate the stock 285/45r22 would have been at almost 2200RPM to be at 75mph. That seems high in the R’s. (1800-2200, 65-75) is paste the torque curve from what I can tell.

Thanks in advance.

This is my 3rd EcoDiesel, 2014 Limited w/3.55, 21 Limited w/3.21, and 23 Limited w/3.92.


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[2021EcoDiesel]

I am currently running Falken Wildpeak AT3Ws in size LT285/65R20 (34.5 inch diameter) and have the speedo calibrated. at 70 mph I sit at just below 1800 RPMs, I don't crack 2,000 RPMs until about 77-78 MPH. At 70 MPH I see about 24-26 MPG.

That having been said when I had my stock tires (Falkens in P275/55R20) I sat at ~2,000 RPMs at 70 MPH. and still saw excellent fuel economy at 26-28 highway. The added resistance of the larger tires offsets the drop in RPMs in my normal driving.

In my personal experience this engine doesn't seem to mind pushing 2k rpm all day long. Current stock Ecodiesels hit their peak torque at 1,600 RPM however even at 2,200 RPM they are pushing 90+% of that peak figure.

 

[jeepin7]

Thank you and agreed the rolling resistance of the LT tire from the P- metric tire will take some out of the calculation. Your set up is the detail I was wanting to confirm.
The tire I am looking at is 5 lbs each lighter than the existing Nitto and back to stock width. Per the GDE curve, stock torque falls off after 3000. Currently, I can run 23-25 highway mpg’s averaging 70-74. But local speed limits have you pushing 78+ to not get ran over. This is equal to 2200-2500rpm. 15-18mpg.

Not trying to get 30MPG, but a few more points would be great.


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[jeepin7]

I went with the 285/55r22 Amp Terrain Pros. I like we’re it put the RPM’s when going down the highway. Love the way it looks! And no rubbing or trimming needed.

What do you think?

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[jeepin7]

Another angle.

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