Diesel Rubicon 3.73 Gearing With Larger Tires?

  1. cyan2

    cyan2 Member

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    More information on the diesel jeep got released this weeks. I have been looking forward to this. It was stated that the gearing ratio for Rubicon is 3.73, rather than the 4.10 on the 3.6 and 2.0. I'm planing to put a set of 35's on the Jeep, which is no issue for the 4.10 gearing on the 3.6 and 2.0. If the 3.0 diesel only comes with 3.73 gear ratio, would that be an issue to put on larger tires?
     
  2. Headbarcode

    Headbarcode Well-Known Member

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    With the higher torque rating, I don't foresee it being an issue to run 35's or even 37's with the 3.73 gearing.

    It would've been nice if they had just left the Rubicon ratios as is. Unfortunately, maximizing fuel economy is the priority.
     
  3. AnnDee4444

    AnnDee4444 Well-Known Member

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    It all depends on where in the RPM range it makes the torque. What it really gets down to is available torque at the axle. The peak numbers don't tell the whole story without the rest of the dyno chart.

    I had a post a few days ago comparing the road force at the tires of a 3.6 manual vs 2.0. I hope to get information on the the 3.0 diesel soon, to see where it stacks up: https://www.jlwranglerforums.com/fo...6-and-manual-vs-auto.38517/page-2#post-856356
     
  4. JLURD

    JLURD Well-Known Member

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    442lb-ft at 1600rpm more than makes up the difference between 3.73 and 4.10 as it pertains to wheel torque.
     
  5. AnnDee4444

    AnnDee4444 Well-Known Member

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    #5 Oct 3, 2019
    Last edited: Oct 3, 2019
    Do you have a source for that power figure? Everything I have seen has not specified a RPM @ maximum torque. I can find where the Ram's 3.0 calls out 1600 RPM, but nothing for the Jeep. I suspect that the Ram & Jeep's 3.0 are both ECU limited like the 2.0 turbo, and would have a wide RPM range where maximum torque is reached (The Ram's 480 lb-ft is exactly 650 NM, Jeep's 442 lb-ft = 600 NM, 2.0 turbo's 295 lb-ft = 400 NM... these even numbers aren't a coincidence). Because of this, I would think that the Jeep's 3.0 would achieve peak torque earlier than the Ram, and hold it longer. This would also explain the identical 260 HP rating (which is 379 lb-ft @ 3600).

    Assuming the gear ratios will be the same (and of course the 3.73 vs. 4.10), here's how the road force of a 2.0 JLUR would compare to a 3.0 JLUR. The 2.0 is the dotted line, and the 3.0 is estimated a portion of the 3.0's torque 'curve' with the solid straight lines. I estimated using the two data points discussed above (442 lb-ft @ 1600 & 379 lb-ft @ 3600).
    Pounds of road foce by gear (1).png
    Edit: fixed the graph to show 8th gear & reverse.
     
  6. AnnDee4444

    AnnDee4444 Well-Known Member

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    Assuming the ECU doesn't limit boost by gear, you could run 40" tires on the 3.0 JLUR and have about the same road force as a 2.0 JLUR.
     
  7. JLURD

    JLURD Well-Known Member

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    I assumed the rpm from the Ram 3.0 figures. The JLU 3.0 may well reach peak torque earlier, but if it does, it won’t be by much. We’ll see.
     
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