JLUR - 4.88 vs 4.10 Gear Review Details

Petey003

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Hi All!

I've got some interesting data listed below as well as looking for first hand experience feedback.

Vehicle: 2018 JL Unlimited Rubicon (auto)
Weight: 5,370lbs (full tank, not in vehicle, all regular gear loaded) which is a gain of +940lbs over original curb weight (4,430)
Tested Altitude: 800ft +/- according to Gaia GPS
Tire Size: 37" General Tire Grabber X3's (79.7lbs)
Math: New tire size (37) divided by original tire size (33) = 1.1212 multiplied by original gear ratio (4.10) = 4.5969.

I realize that the closest gear match would be 4.56 but I'm looking to go 4.88 to compensate for the extra 940lbs + any other mods I add. I'm also in the mountains a lot in the North East (VT, NH, NY, Maine, VA, etc).

I've attached all current RPM results of each gear (6th, 7th, and 8th) and highway speed (65, 70, 75, and 80mph) below with this current set up. (see attached photo).

Does anyone have results of a JL or JLU at highway speeds with 4.88's? I've love to compare prior to my trip to the shop!

Mac 4.10 gearing on 37s.jpg


Thanks everyone!





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Petey003

Petey003

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Your current setup:
37s.png



With 4:88s
4.88.png
Dude, this is GREAT!

Where did you get this or did you create it? I'd love to know!

To confirm, this is factoring my 37s?
 

D60

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800' elevation?? That's all I'd need to feel like I'd bolted a blower onto any of my vehicles!
 
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Petey003

Petey003

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Petey003

Petey003

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800' elevation?? That's all I'd need to feel like I'd bolted a blower onto any of my vehicles!
Haha, that was a drive back into the MidWest to visit fam. I think I was crossing Ohio when I got that reading.

I'm usually in NY, VT, VA, CT, NH so I'm constantly challenged with mountains. Gears first, then maybe when my warranty is gone I'll pony up the cash for a blower!
 
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Petey003

Petey003

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AnnDee4444

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Hey,

Would you mind sending me the link for this as a PM? It looks like it's being edited etc. so it stopped the formulas from working.

Or perhaps send to my email? [email protected]

Thanks man!
Yeah, that's the one downside to doing this in google docs: everyone is sharing the same exact spreadsheet. If more than one person is in it, everyone will be fighting each other for the changes.

Here's how you can download your own copy:
Download.png
 

vavaroutsos

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FYI, for accurate results you need to use dynamic tire size. The bottom of the tire flattens as the tire rolls, which gives an effective dynamic tire size smaller than the static size. The most accurate way to get this number is to calculate it from the tire manufactures revolutions per mile specification. If they don't provide it, I have found that the specified tire diameter less 1.25" is a pretty close guess for the tire sizes typically used on a Jeep.
 

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