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Old 08-13-2012, 10:16 AM   #1
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Gear Ratio for 2013 Auto on 285/70/17

First off, thanks to everyone on this forum. Asked a lot of annoying questions recently but finally pulled the trigger and ordered a 2013 auto JK Rubi.

I've read a ton of threads on the 4.10 vs 3.73 debate, studied the gear ratio chart, and it seems that 4.10s are definitely the way to go if you're throwing 35s+ on, and 3.73s are probably ideal with 32s. I'll be either leaving the stock tires on there or swapping them for 285/70/17 Duratracs, which are are hair smaller than 33s at 32.8. The Jeep will be my DD and will sadly not see a ton of low speed crawling. I stuck with the 3.73s on my order and think I made the right choice, but wondering if anyone has specific thoughts or experience with that tire size as I haven't seen it discussed. I know a ton of people go with the Duratracs in that size so hopefully this will be at least a somewhat helpful thread for others.

Thanks for the help!

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Old 08-13-2012, 10:33 AM   #2
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Well, I have 285-70-17 on my '12 JKU with a 3:21 axle and it seems to be doing the job fine.

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Old 08-13-2012, 10:58 AM   #3
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Originally Posted by MudderNuker
Well, I have 285-70-17 on my '12 JKU with a 3:21 axle and it seems to be doing the job fine.
I am a total newbie and found out about the axle ratio afterwards. Was a little choked cause I almost bought one with the Max Tow Group which has the 3.73. But the 12 JK I did buy was almost $2K less with everything I wanted, so I figure I can regear for that price difference some day if I really feel I want it, and really do it proper (4.88 ratio).
But the 3.23 seems to have plenty of power to me. I am going to go to the dealer though and give them a bit of a hard time (they kind of misled me on Max Tow package option) and see if they will give me a real good deal on regearing. But I am not going to make a huge stink about it.
Love my jeep! Just wish I had found this forum before buying. It rocks.
The way I look at it though is that the jeep was an impulse buy, and at least I am in one, and not a Ford Escape :-)
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Old 08-13-2012, 09:07 PM   #4
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Quote:
Originally Posted by 93TilInfinity View Post
First off, thanks to everyone on this forum. Asked a lot of annoying questions recently but finally pulled the trigger and ordered a 2013 auto JK Rubi.

I've read a ton of threads on the 4.10 vs 3.73 debate, studied the gear ratio chart, and it seems that 4.10s are definitely the way to go if you're throwing 35s+ on, and 3.73s are probably ideal with 32s. I'll be either leaving the stock tires on there or swapping them for 285/70/17 Duratracs, which are are hair smaller than 33s at 32.8. The Jeep will be my DD and will sadly not see a ton of low speed crawling. I stuck with the 3.73s on my order and think I made the right choice, but wondering if anyone has specific thoughts or experience with that tire size as I haven't seen it discussed. I know a ton of people go with the Duratracs in that size so hopefully this will be at least a somewhat helpful thread for others.

Thanks for the help!
Hey, 93!

I'm pretty well known here as a fan of 3.73s with the new auto tranny (manual is a whole different equation) even on Rubis,

IF....

1. You're going to stay near stock size tires (the <33" Duratracks, for instance,)
2. You're not doing a lot of heavy towing,
3. You're not doing most of your driving at high altitude and steep roads (think Rocky Mountains,)
4. You are mostly DD in the flat-lands or moderate hills.

If any of the above don't apply, get the 4.10s

If you want a real, dedicated rock-crawler, get a sport and re-gear and re-axle to Dana 60's, etc.

But, in the end, it's your Jeep, and your decision, you'll love it with either geaing!
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Old 08-14-2012, 12:29 AM   #5
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I just had a teraflex 2.5 suspension lift with 35/12.5/17 pro comp tires and wheels installed on my 2012 COD rubicon. I really do not notice any drop in power. Mine is a auto 5 with 373 rear end. I thought I had dropped a little in mpg but I am still getting 18 mpg driving to work and back which is city, before I saw 18.3 to 18.5. Last week it was 17.5 but I had lots of bumper to bumper traffic on that tank of gas.
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Old 08-14-2012, 01:09 AM   #6
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Originally Posted by Up Hill Bill View Post
Hey, 93!

I'm pretty well known here as a fan of 3.73s with the new auto tranny (manual is a whole different equation) even on Rubis,

IF....

1. You're going to stay near stock size tires (the <33" Duratracks, for instance,)
2. You're not doing a lot of heavy towing,
3. You're not doing most of your driving at high altitude and steep roads (think Rocky Mountains,)
4. You are mostly DD in the flat-lands or moderate hills.

If any of the above don't apply, get the 4.10s

If you want a real, dedicated rock-crawler, get a sport and re-gear and re-axle to Dana 60's, etc.

But, in the end, it's your Jeep, and your decision, you'll love it with either geaing!
Bill,

In your esteemed opinion, what are the disadvantages of going with 4.10s in a Rubicon if some/all of items 1 thru 4 do apply? is it just about gas mileage, or am I missing something?

Thanks,

LarsA
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Old 08-17-2012, 05:24 PM   #7
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3.73 Disadvantages

Hello everyone and thank you for this thread. I also just ordered a Wrangler with the 3.73 gears on the recommendation that I was not:

- immediately lifting the Jeep (plan to go 2.5")
- nor immediately upgrading to 35" tires (I would like to go with 35s)

Specifically, I was also instructed that the 4.10 would only be applicable for slower 4WD travel and max-towing. I off-road to consider a Rubicon, but not as often and to the extent many on this list do. Additionally, I drive A LOT of highway, so even a couple extra MPG will make a difference. Hence, why I chose the 3.73.

After reading these posts, I am concerned though...

- 35s are too big. 33s tops?
- Is it worth raising the Jeep if that's the case?
- What is this about high altitude driving?

I do a lot of climbing and skiing and travel frequently to the high country. How does this gear setup affect that driving, unless only referring to difficult off-roading?

A VIN is assigned to my order, meaning it is not possible to change the order. Did I make a costly mistake? Ultimately, what I want to do, is maintain an ~17 MPG, be able to pretty much go off-road where ever I want to, but not to extent of major rock-crawling (yet), and have a good looking vehicle that's eye catching while being functional.

Thank you for the responses in advance!

-FRANK
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Old 08-17-2012, 07:35 PM   #8
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Frank, Welcome Aboard! I have the 3.73 ratio with 6 speed and running 285/70-17s (33s). I live in Colorado and we have a few hills here (LOL) and I have no lack of power.
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Old 08-21-2012, 12:03 PM   #9
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Thanks, SilverSport! Those Colorado hills make AZ mountains look like termite piles. Glad to hear about your Jeep's performance. Is yours also lifted?
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Old 08-21-2012, 12:27 PM   #10
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I would make sure to choose a "P" version of the 285/70-17 tire. If you do this, they will only add about 5 lbs. per corner compared to the stock Rubicon tires. You won't notice much hit to MPGs.

However, if you switch over to light truck tires (LT) and go with a "D" or "E" rated version, you'll add significant weight and your MPGs will decrease 2-3 miles per gallon which is equivalent to about $60/month for the average driver.

The 3.73s are actually perfect for you since you travel the highways a lot. 4.10s are pretty deep and would put you beyond 2,500 RPM on the interstate which is not where you want to be.
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Old 08-21-2012, 12:51 PM   #11
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My kid has an 11 jkus, we swapped tires for a week. He lost 2MPG, I gained 2...

His 18 combined went to 16, my 15 around town went to 17.

I have 4.10, his is 3.73.

His comment when driving mine- "wow, this jeep hauls ass"

My comment after he returned from a road trip - " wow, 22 mpg, unheard of here, best I get is 20 at 60 mph, 17 at 70".

Just more FYI
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Old 11-08-2012, 07:40 AM   #12
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2013 Auto Gears

Greetings to all,

So I have decided to trade my 2010 Sport manual in for a 2013 Sport Auto. Yeah it was a hard decision but I really like the ease of driving with the auto. Anyway, moving on from that. Has anyone seen the gear ratios for the new 2013 Wrangler Sport? The old timer working at my local dealer ship said the 2013s are running a 3.55:1 ratio in the Sports now and the one I test drove, and coincidently will be purchasing later today, lol, even with the lift and larger tires was pulling something serious.
My question is this: Has anyone actually heard what the gear ratios are for sure on the 2013 Sport models? Thanks
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Old 11-08-2012, 10:49 AM   #13
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Bill,

In your esteemed opinion, what are the disadvantages of going with 4.10s in a Rubicon if some/all of items 1 thru 4 do apply? is it just about gas mileage, or am I missing something?

Thanks,

LarsA
Ive been wondering this, also how much of a difference is it between gpm?
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Old 11-09-2012, 01:04 PM   #14
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Ive been wondering this, also how much of a difference is it between gpm?
Anyone?
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Old 11-09-2012, 01:07 PM   #15
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Originally Posted by jeeper4life73 View Post
The old timer working at my local dealer ship said the 2013s are running a 3.55:1 ratio in the Sports now and the one I test drove, and coincidently will be purchasing later today, lol, even with the lift and larger tires was pulling something serious.
My question is this: Has anyone actually heard what the gear ratios are for sure on the 2013 Sport models? Thanks
The old timer was wrong. It's the same as it's always been for Sports--3.21 or 3.73.

Quote:
Originally Posted by LarsA View Post
Bill,

In your esteemed opinion, what are the disadvantages of going with 4.10s in a Rubicon if some/all of items 1 thru 4 do apply? is it just about gas mileage, or am I missing something?

Thanks,

LarsA
Quote:
Originally Posted by stoop14 View Post
Ive been wondering this, also how much of a difference is it between gpm?
There are gear ratio charts floating around on this site that show the RPM difference at 70 mph. You can also find a calculators online that allow you to calculate the RPM difference at any speed.

The numerically higher the gears (often called "deeper" or "lower"), the faster and higher the RPMs will rise, meaning that you will both take off faster and pull harder once at speed. For offroading, this also means that your RPMs will be higher when crawling slowly, increasing your power despite progressing at a very slow speed.

The trade off of for all these benefits of numerically higher gears is that, in general, you use more fuel and run at higher RPMs.
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Old 11-10-2012, 01:01 AM   #16
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Does running at higher rpms constanty hurt your engine? if i got 4.10 and never put larger then 33" tires on would it damage/increase wear on the engine over the long run?
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Old 11-10-2012, 01:17 AM   #17
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Originally Posted by stoop14
Does running at higher rpms constanty hurt your engine? if i got 4.10 and never put larger then 33" tires on would it damage/increase wear on the engine over the long run?
I'd expect it would be negligible.

It's only a difference at any one time of a few hundred RPM in a motor that redlines at something like 6000 RPM. And even though it's sometimes easier on components to go slower, it's sometimes more mechanically efficient to go faster.

I wouldn't think it would be significant.
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Old 11-10-2012, 05:45 PM   #18
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I had a 12 Sport with 3.21s. Went to Colorado with it. Highway was great at 22 mpgs but as soon as we got close to the mountains, I was looking for lower gears. It suck. Got to Colorado, could barely make it up Pikes Peak if we pulled over to site see. Had to use 4L or get a running start to get up our driveway. Came home and traded it in on a 13 Rubi w 4.10s. Headed back to Colorado for Thanksgiving with no regrets.
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Old 11-22-2012, 10:10 PM   #19
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What are the MPG people are getting on their 2012-13 Rubicons with 4.10?
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Old 11-22-2012, 10:58 PM   #20
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2013 Rubicon owner here: getting around 15.6 - 15.8 mpg with 4:10 gears and an automatic. I have been driving mostly around town, then 75 miles to deer camp and then some time on a trail in the woods. Not bad for a vehicle with 1800 miles and the capabilities of this thing.
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Old 11-23-2012, 07:53 AM   #21
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"My kid has an 11 jkus, we swapped tires for a week. He lost 2MPG, I gained 2..."

12JKUR, what was the tire sizes that y'all swapped ?

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