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Discussion Starter · #1 ·
I have seen countless threads about gears and tires but, to many conflicting thoughts between 4.88s and 5.13s. I have an 08 unlimited X thats gettting a make over here soon to make it look a little more like a Jeep. 2.5 max travel lift, 35s, 17in wheels, winch, fenders blah blah right. This Jeep will be 90% street driven and my wifes rig on top of that and she says she will kill me if the MPGs get bad. So after reading the gear chart and seeing 5.13s I have to ask, those just seem so low! Like I said this is a street rig I have a YJ on Rockwells to cover the trails I am just looking for the right gears to get this thing back to stock.
 

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One important information missing in your post: Auto or Standard?

Your MPG will take a hit no matter what due to weight and added wind resistance of your mentioned mods.
What type of driving will be mainly done, city, highway,...?
What's the environment you're driving in, elevation, flat or hills,....?
 

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Discussion Starter · #3 ·
One important information missing in your post: Auto or Standard?

Your MPG will take a hit no matter what due to weight and added wind resistance of your mentioned mods.
What type of driving will be mainly done, city, highway,...?
What's the environment you're driving in, elevation, flat or hills,....?
You know I said to my self make sure to type that info but I did forgot sorry. It is an auto, and the driving will be city/highway ( I want to be able to take road trips). I live a some what hilly environment Louisville Ky doesnt know how to make flat roads there is always random hills.
 

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Different gears will not get you back to stock mpg's. You are putting on heavier tires that create more resistance and you are getting it another 5+ inches off of the ground which will cause more drag. The correct gears for the tire size will put you back in the optimum rpm range which gives you power where you need it but you are still loading the engine more with bigger tires and that is the main thing that kills the fuel mileage.

With that said... From my extensive reading on fuel mileage, gears, and tire size and deciphering through all of the bs, you will probably get better fuel mileage from 4.88’s and 35’s but you will see more power from 5:13’s and 35’s. Much like 3.73’s give better fuel mileage on a stock JK but 4.10’s give better performance.
 

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Different gears will not get you back to stock mpg's. You are putting on heavier tires that create more resistance and you are getting it another 5+ inches off of the ground which will cause more drag. The correct gears for the tire size will put you back in the optimum rpm range which gives you power where you need it but you are still loading the engine more with bigger tires and that is the main thing that kills the fuel mileage.

With that said... From my extensive reading on fuel mileage, gears, and tire size and deciphering through all of the bs, you will probably get better fuel mileage from 4.88’s and 35’s but you will see more power from 5:13’s and 35’s. Much like 3.73’s give better fuel mileage on a stock JK but 4.10’s give better performance.
You can get the same mpg with different gears just not at the same speed :thefinger: (damn tapatalk and its lack of emocons)

Sent from my DROIDX using Tapatalk
 

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Very True !!

But do you really want to get pulled over for going toooooo slo !!!
:shaking:
 

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Discussion Starter · #8 ·
Let me clear this up a little I am not trying to get back to the stock MPGs and trust me I understand what happens to fuel when you lift a rig. That being said I dont want to see MPG drop to 9-10.
 

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From what I have read and deciphered through you can get 15 to 17 with 4.88’s and 13 to 14 with 5.13’s. Personally I rather have a little more power than a little better fuel mileage, and I pull a trailer some, and it's not flat here so I will be going 5:13's. There are folks that say they get better but I don’t believe them :thefinger:
 

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Discussion Starter · #10 ·
From what I have read and deciphered through you can get 15 to 17 with 4.88’s and 13 to 14 with 5.13’s. Personally I rather have a little more power than a little better fuel mileage, and I pull a trailer some, and it's not flat here so I will be going 5:13's. There are folks that say they get better but I don’t believe them :thefinger:

13/14 is pretty close to stock. The dealer window sticker says 15 city. So lose a mile or two and gain performance! How is it on the highway though? I dont want the engine turning 3k.
 

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The difference between 4.88's and 5.13's at 60 mph is something like 100 rpm. In a hilly area I'd go with 5.13's as it puts you in the power band a little better.
 

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I am doing the exact same lift, and tire choice as you, living in COlorado with the (x) auto, I eleccted to go with the 5:13 gears.
 

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You know I said to my self make sure to type that info but I did forgot sorry. It is an auto, and the driving will be city/highway ( I want to be able to take road trips). I live a some what hilly environment Louisville Ky doesnt know how to make flat roads there is always random hills.
I'd say you'll be fine going to "just" 4.88 with the KY topography.
 

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13/14 is pretty close to stock. The dealer window sticker says 15 city. So lose a mile or two and gain performance! How is it on the highway though? I dont want the engine turning 3k.


That's all you're getting stock?? I averaged around 19 between highway and city before my lift and 33's. I have 3.73 gears and average around 15.5 consistently now.
 

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Bone stock I got 14-15 avg in windy west Tx hill country.
Now w 37s on humvee wheels, LOTS of extra weight and 5.13s I get 12-13


Scratched into the wall with a dead iPhone.
 

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Discussion Starter · #16 ·
To be honest I havent even ran a hole take of gas through the rig yet! The sticker said 15 city. I am going to go with 5.13s. I will be going bigger than 35's but I will be replacing the front and rear axle then so I will regear then.
 

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Gas mileage is what it is. If you don't want to lose it, get the Eibach lowering kit and get smaller tires. Throw some 3.21's in it with low profile tires and hug those corners.... :D

Seriously, 4.88's or 5.13's. Either one will work. Since you're "worried" about the mileage, just go with 4.88's.
 
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