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Old 10-11-2012, 11:53 PM   #1
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4.10 vs 3.73?

Going to pick up a new 2013 rubicon with auto tranni, how big of a improvment is the 4.10 for off roading? How much will it kill my mpg?

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Old 10-12-2012, 12:17 AM   #2
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Old 10-12-2012, 12:38 AM   #3
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Just have my JKUR with 4:10s for a week. Got about 200 miles on it and I am getting about 15 mpg.
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Old 10-12-2012, 04:04 AM   #4
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Just have my JKUR with 4:10s for a week. Got about 200 miles on it and I am getting about 15 mpg.
Yikes I get better mileage than that and I run 35" tires, lift, and my lower plastic skid has been removed.
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Old 10-12-2012, 06:09 AM   #5
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Yikes I get better mileage than that and I run 35" tires, lift, and my lower plastic skid has been removed.
Me too. Plus, I drive like a carjacker. Get high 15's, low 16's generally...
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Old 10-12-2012, 06:25 AM   #6
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Just have my JKUR with 4:10s for a week. Got about 200 miles on it and I am getting about 15 mpg.


Got in the 15's for my first tank, after 500 miles i'm getting 18's. 2013 JKUR 4:10s manual
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Old 10-12-2012, 07:39 AM   #7
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You're only talking a couple hundred RPM difference. The only place it's going to kill your mileage is on the interstate highways. Otherwise, it'll actually do better around town and on the trails.
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Old 10-12-2012, 07:49 AM   #8
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Lot of cash for swapping ratios for f-all difference between those ratios if you had to. Gladly you were wise on initial purchase.; ) enjoy your new rig!
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Old 10-12-2012, 07:54 AM   #9
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I have 4.10, but would get 3.73 next time. Since it's a rubicon it comes with a 4:1 transfer case. So offroad in low, it winds out quickly. If it wasn't a rubicon and had the 2.71 case, 4.10 would make more sense.

4.10 on the freeway drinks a lot of gas. If you were going to run 37's though, 4.10s would be my choice.
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Old 10-12-2012, 08:00 AM   #10
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If you plan on getting bigger tires then get 4.10. And most of us end up with bigger tires in the end. I found that once I regeared mine to 4.88, that bigger tires actually worked better with mileage. My last set of tires were .72" taller then my current set and I got 1mpg more with that tire. Also towing benefits from the 4.10 over the 3.73

If you never plan on getting bigger tires, then the 3.73 will get you by but it seems that modding a Jeep is an addiction and bigger tires just seem to happen in the end. I said I would never go lareger then 33's but my next set will be 35's
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Old 10-12-2012, 08:28 AM   #11
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We get 18-19 with 3.73s and 33s. If a Rubicon on stock tires is only getting 15 there is something wrong.
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Old 10-12-2012, 08:37 AM   #12
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We get 18-19 with 3.73s and 33s. If a Rubicon on stock tires is only getting 15 there is something wrong.
That could just be based on the weight of the foot on the accelerator.
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Old 10-12-2012, 08:41 AM   #13
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You're only talking a couple hundred RPM difference. The only place it's going to kill your mileage is on the interstate highways. Otherwise, it'll actually do better around town and on the trails.
Agreed, highway mileage is horrible. I commute daily with mostly highway driving and I'm averaging in the high 15's



Its alway hard for me to believe guys that say they are getting 18-19 running 4.10. I'm completely stock, always try to keep it under 3k rpm (Eco mode) and The absolute best average I ever saw was in the low 17's. I have actually been reading that guys running 33's with 15" rims are getting better mileage because the RPMs are much lower and the 4.1 seems to be better paired with that set up than it does with stock.
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Old 10-12-2012, 09:14 AM   #14
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That could just be based on the weight of the foot on the accelerator.
Yes, but that isn't the fault of the vehicle. That is the driver only getting 15, not the vehicle only getting 15. A Honda Civic will get 15 if you flog it hard enough.
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Old 10-12-2012, 09:24 AM   #15
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Yeah, I mean, with 3.73s and stock tires I was turning 2,300 RPM on the interstate at the speed limit. So with 4.10s I'd have been turning at least 2,500 RPM or closer to 2,800 RPM if I was speeding just a little bit. That is insane RPM to be turning when you've got 285 horsepower under hood. It's a waste of fuel and it's hard on the longevity of the engine.

That's why you should only do 4.10s if A) you're sure you're going to run larger tires or B) you're sure you won't be on the interstate highways much.

I honestly feel like 3.55 would be a perfect ratio for these JKs in stock form...but that isn't offered anymore. So I got 3.73s.
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Old 10-12-2012, 09:24 AM   #16
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Agreed, highway mileage is horrible. I commute daily with mostly highway driving and I'm averaging in the high 15's



Its alway hard for me to believe guys that say they are getting 18-19 running 4.10. I'm completely stock, always try to keep it under 3k rpm (Eco mode) and The absolute best average I ever saw was in the low 17's. I have actually been reading that guys running 33's with 15" rims are getting better mileage because the RPMs are much lower and the 4.1 seems to be better paired with that set up than it does with stock.
Believe it. I routinely get 18-20 mpg with my 2dr 6spd. 3.8 Rubicon, hwy, doing the actual math. I'm running stock tires and wheels with off road bumpers and a winch. Any JK getting only 15mpg that's basically a stock set up, something's wrong.
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Old 10-12-2012, 09:25 AM   #17
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Its alway hard for me to believe guys that say they are getting 18-19 running 4.10.
I routinely get 18+ mpg in my stock JK...which is an '09 with the 3.8 liter engine in it!

I actually expect my MPGs to go down in my new JK because it's an automatic.
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Old 10-12-2012, 09:46 AM   #18
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If your going to get bigger wheels, 4.10 is a no brainier. If your going with the stock wheels then I would consider how much interstate driving your going to be doing, and what kind of off-roading your planning on doing. With mud and sand the transfer case is pretty darn low.

GEAR TO MPG GUESS
After reading through about a dozen MPG threads my personal guess is that the average mpg for road driving work out close to this.
3.21 = 21
3.73 = 19
4.10 = 17

4:10 MPG AT RPM RANGE
I've got a 2012 6-speed manual Rubicon with the stock wheels and 4.10's. I did a road trip a few months back, and I tried to find the best speed for the highest mpg to pass the time. I used the AVG MPG off the wheel to test resetting every so often at different speeds. This is not exact but the best of my testing ability and memory. They are all 6th Gear on very flat 1-65 Indiana interstate.
80mph - 15.5 mpg - 2750 RPM
70mph - 17mpg - 2400 RPM
65mph - 19mpg - 2200 RPM
45-55mph - 22mpg - under 2000 RPM
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Old 10-12-2012, 09:55 AM   #19
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so what is the differnce? Im a mechanical noob
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Old 10-12-2012, 10:07 AM   #20
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Believe it. I routinely get 18-20 mpg with my 2dr 6spd. 3.8 Rubicon, hwy, doing the actual math. I'm running stock tires and wheels with off road bumpers and a winch. Any JK getting only 15mpg that's basically a stock set up, something's wrong.
Sorry, I don't. How are you calculating your MPGs, the trip computer? According to my Jeep's trip computer I'm almost always in the 17's but in real world I'm far from it. Even with a manual transmission, I'll believe high 17's but that's it. No where near 20, sorry.

The fact is that the 4.1 ratio will be spinning at higher RPMs if your running stock tires, that equates to more gas. If your consistently on a highway that means worst gas mileage, simple as that. You can try to offset that obviously by not over revving and trying to keep it on the highest gear but no matter what you do, you wont be able to beat the physics.

I religiously keep track of my MPG, through real world numbers at every fill up, the only factor that deviates the mileage is fuel blend switch-over from summer to fall and the quality of gas. I was seeing a 1-2 mpg fluctuation when I switched from Wholesale Club (BJs) gas to Exxon. Sure the wholesale gas was a couple of cents cheaper/gallon but I was losing mpg and it was a wash so I just use the same Exxon gas from the same station and things have been steady.
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Old 10-12-2012, 10:37 AM   #21
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Yeah, I mean, with 3.73s and stock tires I was turning 2,300 RPM on the interstate at the speed limit. So with 4.10s I'd have been turning at least 2,500 RPM or closer to 2,800 RPM if I was speeding just a little bit. That is insane RPM to be turning when you've got 285 horsepower under hood. It's a waste of fuel and it's hard on the longevity of the engine.

That's why you should only do 4.10s if A) you're sure you're going to run larger tires or B) you're sure you won't be on the interstate highways much.

I honestly feel like 3.55 would be a perfect ratio for these JKs in stock form...but that isn't offered anymore. So I got 3.73s.
I'm thoroughly confused on this topic. I've looked at the gearing charts posted on other threads, and it looks like with the 4.10s and auto transmission, the 32 inch factory tires are about as big as I should go. I was planning on putting 33s on next year. Would 35s work better with this gearing or am I missing something?
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Old 10-12-2012, 10:40 AM   #22
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My 2-door Rubicon is pretty stock still, haven't been able to start any major mods yet. So, I still have the stock rims and tires, no heavy bumpers, etc. I have a 6-speed with the 4.10 rear and my drive consists of about 20-miles of 4-lane highway at 65-mph, with the last 4 to 5-miles of city driving. I average about 19.5-mpg overall. If I take back roads to work and keep my speed to 55-mph, it will boost my mileage to nearly 22-mpg, sometimes even better than that. When I am on the highway, I throw it in sixth and set the cruise, so I keep my foot out of it for the most part.
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Old 10-12-2012, 11:31 AM   #23
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Sorry, I don't. How are you calculating your MPGs, the trip computer? According to my Jeep's trip computer I'm almost always in the 17's but in real world I'm far from it. Even with a manual transmission, I'll believe high 17's but that's it. No where near 20, sorry.
It's easy, miles driven divided by fuel used. Our trip computer is almost always within 1/2 mpg either way. You have the unfortunate disadvantage of being at sea level where mileage is at its worst, but it should still be better than 15. When we were in Colorado a few months ago we got 22-24 mpg in the thin air. The only thing that seems to change our mileage is how far we push the pedal. It sits at 18-19 mpg all the time unless we get out on the highway running 75-80 mph. Once we get past 70-75 it plummets.

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The fact is that the 4.1 ratio will be spinning at higher RPMs if your running stock tires, that equates to more gas. If your consistently on a highway that means worst gas mileage, simple as that. You can try to offset that obviously by not over revving and trying to keep it on the highest gear but no matter what you do, you wont be able to beat the physics.
RPM has very little to due with mileage any more. As long as the engine is running at or near its torque peak the only change in the equation is the extra friction from spinning the engine and drivetrain a little faster. That friction is minimal compared to the wind and rolling resistance. You would have to have lab quality equipment to measure it.
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Old 10-12-2012, 11:31 AM   #24
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Sorry, I don't. How are you calculating your MPGs, the trip computer? According to my Jeep's trip computer I'm almost always in the 17's but in real world I'm far from it. Even with a manual transmission, I'll believe high 17's but that's it. No where near 20, sorry.

The fact is that the 4.1 ratio will be spinning at higher RPMs if your running stock tires, that equates to more gas. If your consistently on a highway that means worst gas mileage, simple as that. You can try to offset that obviously by not over revving and trying to keep it on the highest gear but no matter what you do, you wont be able to beat the physics.

I religiously keep track of my MPG, through real world numbers at every fill up, the only factor that deviates the mileage is fuel blend switch-over from summer to fall and the quality of gas. I was seeing a 1-2 mpg fluctuation when I switched from Wholesale Club (BJs) gas to Exxon. Sure the wholesale gas was a couple of cents cheaper/gallon but I was losing mpg and it was a wash so I just use the same Exxon gas from the same station and things have been steady.
Like I mentioned, I do the math. I don't go by the computer, even though at times the computer is off only approx. .5 or 1 mpg because of averaging I guess. I only run Shell 87 octane. I get approx. .5 to 1 mpg less with a winter blend fuel on average I found. Maybe I keep a lighter foot and 6th gear more, who knows. The 10 Rubicons only come with 4.10's as you know so that's not it. No 2 JK's are alike I guess. EPA and real world averages are averages I guess.
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Old 10-12-2012, 11:44 AM   #25
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Yeah, I mean, with 3.73s and stock tires I was turning 2,300 RPM on the interstate at the speed limit. So with 4.10s I'd have been turning at least 2,500 RPM or closer to 2,800 RPM if I was speeding just a little bit. That is insane RPM to be turning when you've got 285 horsepower under hood. It's a waste of fuel and it's hard on the longevity of the engine.

That's why you should only do 4.10s if A) you're sure you're going to run larger tires or B) you're sure you won't be on the interstate highways much.

I honestly feel like 3.55 would be a perfect ratio for these JKs in stock form...but that isn't offered anymore. So I got 3.73s.
^This x 1000
I would love 3.55's....
And unless you plan on modding, or live in a very hilly area, or do very litle highway driving, 4.10's coupled with the new auto is a lot of gear for a DD.

RPM's in 5th gear on stock 32.06 inch wheels at 70 mph with NAG-1 auto:
4.10 = 2497
3.73 = 2271
3.55 = 2162
3.21 = 1955

Manuals have a little longer top gear, so it isn't quite as bad on the highway.
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Old 10-12-2012, 12:18 PM   #26
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I will say that the mpg at 65 mph vs 70+ mph is the difference some people see. I live in the so I go up and down hills and can get 19+ mpg going 65 mph or 17ish going 70+ mph and I have 4.10s
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Old 10-12-2012, 03:49 PM   #27
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Old 10-12-2012, 07:44 PM   #28
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had my JKR w/4.10s for a week now. averaged 16.5 on the first tank and 135 of that was highway. seeing about 15 mpg this week, no highway. all in all i like it better than that 2010 Sahara w/3.73s i traded in
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Old 10-15-2012, 12:10 AM   #29
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whats the biggest tires to run on 3.73 its hard to find a auto with 4.10 up here!!!
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Old 10-15-2012, 02:03 AM   #30
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whats the biggest tires to run on 3.73 its hard to find a auto with 4.10 up here!!!
I have 37s on mine and its a 2012 the gas is horrible though 12.5 hwy 14 with the wind and 9.5 city

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