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488s or 456s. That is the question

LostWoods

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So I believe this was true for the JK D44 axles, but I'm fairly certain the AdvanTEK D44's in the JL/JT all use the same 8 tooth pinion for 4.88, 5.13 and 5.38. Only the tooth count on the ring gear changes (39, 41, and 43 respectively). 4.56 has a 9 tooth pinion and the 4.10 picks up 10 teeth. Don't quote me on that as Dana has updated their site and it no longer lists the specifics for any ratio above 4.10, but you can count the teeth in the pictures lol. Agreed thought... you should be fine unless you are going crazy. In that case, take a look at dynatrac or currie axels.

https://spicerparts.com/parts/axle/...ring-and-pinion-gearing-for-jeep-gladiator-jt
I think you are entirely right on that... I know I saw a site that gave the actual counts at one point but I've never been able to find it again. I did count on each image and they translate exactly to the correct ratios. That's probably why I've been dead set on 5.13 for so long because if 4.88 has the same pinion, what's the point of going shallower if the risk is all the same?
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Youā€™re welcome to come drive mine too. I think everyone here who has done gears went through what you guys are debating. The data doesnā€™t necessarily add up to the real world outcome. There are just so many variables that affect the experience. I was originally going with 4.88ā€™s for 37ā€™s because I was so worried about 5.13ā€™s based on charts and calculators. Now look at me wishing I had gone 5.38ā€™s.
I have 5.13s ordered for my 6spd and 38s. Should I have gone with the 5.38s?
 

WK2JT

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I have 5.13s ordered for my 6spd and 38s. Should I have gone with the 5.38s?
You will be fine, especially in NY. The 5.13ā€™s are a great improvement and you wonā€™t go wrong with them. You have the benefit of controlling your transmission gear and RPM. Plus the manual trans overdrive is slightly less than that is the auto. Itā€™s just hard to go too deep on the JL/JT vs older platforms. The transmissions have such a wide range now. You used to make a compromise for craw/drivability vs highway driving, but that has been greatly reduced now.
 

FR33DOM

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37ā€™s with 5.13ā€™s and soooo regretting I didnā€™t go 5.38ā€™s. MPG actually got better with the 5.13ā€™s over the stock 3.73ā€™s and itā€™s just getting into the sweet spot power wise when cruising 70ish. Jeep has to make compromises for various regulations, blah, blah, blahā€¦ you donā€™t when you modify. Regearing is not a linear exercise because of additional rotational mass and leverage acting against you with a larger tire radius. Also, RPMā€™s werenā€™t even optimal when stock so that shouldnā€™t be your measuring stick in my opinion. I went for drivability and the 5.13ā€™s w/ 37ā€™s are nice, but Iā€™ve also driven one with 5.38ā€™s and it was even a little betterā€¦ wish I wouldnā€™t have driven it now.
I too have second guessed 5.13s and many times wished I'd gone 5.38s. Everyone afraid to go too deep but no one actually regrets it when the go to the deep end...
 

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PeterGriffin

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I'm glad to see that altitude is being mentioned as a consideration. As far as elevation goes, do you live there or just visiting? My '17 JKUR on 35s on stock 4.10s at nearly 7K feet of elevation in Flagstaff felt like a rocket at sea level but now that I've moved back to near sea level in SW AZ and will be visiting N/AZ occasionally I'm thinking 4.88s with 35s will work best for me, especially considering that I'll be towing around 3500 pounds with my buggy/trailer.

I never understood going through the expense of a gear change just to go up one "size"; 4.10s to 4.56s doesn't make sense to me personally and I think unless you go a minimum of two sizes, especially is you're jumping up a tire size or two, is necessary to balance things out. Another thing to keep in mind with these tire calculators, which are great tools, is to check the actual, not stated size of the tire. While I love my KO2s their 35s are actually barely over 34 (34.1 to be exact to get my displayed MPG match GPS speed) so keep that in mind too. I'm by no means whatsoever an expert and there's been some great advice already given so far in this thread, just throwing in my 2-cents FWIW...
 
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Gremlinsteve

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How are you liking the 488's and 35's? What rpm are you turning at 75mph? I've got a manual JLUR with the 6 speed and am deciding between 4.56 and 4.88's. It's not bad now with 4.10, but I just want 6th gear to be more usable without making 1st too short. Right now I'm thinking 4.56's are the sweet spot, but haven't heard from anyone running 4.88's until now. I'd love to hear your feedback after living with it a bit.



Loving it. Iā€™m finding Iā€™m in eight gear at about 42-45 mph usually. Rpm at 65 is 2k
 

DanW

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Loving it. Iā€™m finding Iā€™m in eight gear at about 42-45 mph usually. Rpm at 65 is 2k
I just ordered 4.56's. I know if I had the heavier Gladiator I would have gone 4.88's. I'm really looking forward to being able to pull 6th gear like it should instead of limiting to flat land or down hill. It'll also turn 5th into a better hill climber on the highway, particularly in the mountains.

Next up will be the Master Overhaul Kits. I'll order those Monday or Tuesday. I'm wanting to see if Northridge will price match another vendor that is significantly cheaper.
 

Tufelhundin

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Loving it. Iā€™m finding Iā€™m in eight gear at about 42-45 mph usually. Rpm at 65 is 2k
Iā€™m running 315/70-17 with 4.56 and Iā€™m in 8th around 43mph as well.

Right at 2k at 65mph

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DanW

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I see 8th is 0.67 ratio, which is a little taller than the 0.72 in the manual, so it should be pretty close.
 

Tufelhundin

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Gremlinsteve

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A plus is Iā€™m still maintaining 18 plus ā€˜mog
 

DanW

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4.56 gears are going in on Tuesday! I can't wait to drive it!

Any break-in procedure? I'm thinking just drive gently and vary the speed, then I'll probably change the fluid around 5 to 7k miles.

I also have to remember to set the Tazer to the new ratio.
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