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Old 03-20-2012, 03:53 PM   #1
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Pre 2012 4.88 vs 4.56

Found two threads on this but both were in the TJ section. Regarding each of these for the JK, which would prove to be the best ratio for a set of 35x12.5R15 BFG ATs? It's gonna go on a 2010 manual tranny. I've seen the gear chart a bunch and had decided on 4.88s but after reading more into it, there are a large number of people using 4.56s with better MPG and crawling speed than the latter. Most even have heavier tires than the ATs I'm looking at.

Ideas + opinions?

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Old 03-20-2012, 03:57 PM   #2
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Personally I am going 5.13's. There are some on JKowners with 5.38's and 35's but that is auto trans. Mine is auto trans too. With your manual trans I would say 4.88. As long as you don't get 37" tire envy...lol

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Old 03-20-2012, 04:02 PM   #3
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I of course have no actual experience as I haven't regeared my jeep or even driven somebody else's that's been regeared. So my opinion is based on the same chart you've seen a hundred times and reading chatter on forums.

Either would be an improvement, but my vote for 35s on a pre-2012 manual trans would be 4.88. About 2700 RPMs at 70 mph sounds about right, and you don't have the 4:1 t-case that a Rubi would while in 4Lo.

In my mind, the "debate" on this topic is harder fought when you're running 33s. At that point, 4.56 is closer to spot on and 4.88 runs a little high. But at 35, I'd say 4.88.

Just my two cents.
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Old 03-20-2012, 04:05 PM   #4
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I have a 2010 sport manual tranny with a 3.25 coil lift & 35" BFG AT's, I had the 3:21 gears last week I replaced those with 4:88's. Now I have use of all my gears. Even in 6th I have some pep now.
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Old 03-20-2012, 04:07 PM   #5
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Old 03-20-2012, 04:08 PM   #6
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Quote:
Originally Posted by MTH View Post
I of course have no actual experience as I haven't regeared my jeep or even driven somebody else's that's been regeared. So my opinion is based on the same chart you've seen a hundred times and reading chatter on forums.

Either would be an improvement, but my vote for 35s on a pre-2012 manual trans would be 4.88. About 2700 RPMs at 70 mph sounds about right, and you don't have the 4:1 t-case that a Rubi would while in 4Lo.

In my mind, the "debate" on this topic is harder fought when you're running 33s. At that point, 4.56 is closer to spot on and 4.88 runs a little high. But at 35, I'd say 4.88.

Just my two cents.
I think your probably right Mike. I think I'm trying to arguing against 4.88s to make sure I'm correct about choosing them. There are some over at JKO who run 4.56s and talk about how perfect they are too for 35s. I guess it depends on the weight of the tire a lot and this is why I'm wondering? The BFG ATs are 54lbs each.
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Old 03-20-2012, 04:09 PM   #7
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4:88's or 5:13's

5.13's

I know nothing
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Old 03-20-2012, 04:24 PM   #8
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I think your probably right Mike. I think I'm trying to arguing against 4.88s to make sure I'm correct about choosing them. There are some over at JKO who run 4.56s and talk about how perfect they are too for 35s. I guess it depends on the weight of the tire a lot and this is why I'm wondering? The BFG ATs are 54lbs each.
And I guess that's the real issue--they'd both be improvements and neither is likely to be out of the realm of reasonable, so a survey of folks who've chosen either one would likely only reveal that people are generally happy with their choice.

But how many of the respondents do you think would have actually driven both and would be making their recommendation based on a comparison of 4.56 to 4.88, rather than just a comparison of what they chose (4.56 or 4.88) to their original 3.21s (or 3.73s or 4.10s)?

I think weight comes into play, but the diameter is going to be what drops your RPMs. Even if your new 35s are made of mystery material that only weighs 5 pounds, you'd still only be at 1800 RPMs at 70 mph in 6th with your 3.21s. So to me, the weight issue factors in when I think about adding a "little extra" in the RPM department to get me more or less back where I was, but that's about it.

Tough call. One argument for 4.56s would be that if you ever elected to go back to 33s for whatever reason, you'd still have a reasonable highway vehicle. If you had 4.88s in that scenario, you couldn't break 70 mph without exceeding 3k RPMs. You'd be reaching for "7th gear."

Have you tried downshifting and varying your speed on the highway to get a feel for what it's like driving long-term at ~2800 RPMs versus ~2600 RPMs?
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Old 03-20-2012, 04:25 PM   #9
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Quote:
Originally Posted by kjeeper10 View Post
4:88's or 5:13's

5.13's

I know nothing
I think with an auto trans 5.13 will be the cats pajamas.

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Old 03-20-2012, 04:32 PM   #10
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Quote:
Originally Posted by Swamp dogg View Post
I have a 2010 sport manual tranny with a 3.25 coil lift & 35" BFG AT's, I had the 3:21 gears last week I replaced those with 4:88's. Now I have use of all my gears. Even in 6th I have some pep now.
Good info here. Do you spend a lot of time on the highway? Is your Jeep a daily driver?
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Old 03-20-2012, 04:35 PM   #11
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On the interstate now with my 33x12.5R15s I never touch 6th gear and maintain on 65mph for long or short trips. I never have to down shift from 5th for any size hill and can keep the jeep locked into 65mph while getting around 18.5+ in the mpg department.
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Old 03-20-2012, 04:49 PM   #12
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Quote:
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On the interstate now with my 33x12.5R15s I never touch 6th gear and maintain on 65mph for long or short trips. I never have to down shift from 5th for any size hill and can keep the jeep locked into 65mph while getting around 18.5+ in the mpg department.
Thats the tire size I have on my 07 with 4:10 gears and Auto Trans. been pushing the idea of regearing when I get my lockers next year. It is a rough choice. Not sure if it is worth the $$ to regear
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Old 03-20-2012, 05:31 PM   #13
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If you have a PRE-2012 and auto, don't even consider any ratio shorter than 4.88--

Should be 5.13 and if Ruby 5.38--there's no argument !

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Old 03-20-2012, 05:37 PM   #14
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Quote:
Originally Posted by JIMBOX
If you have a PRE-2012 and auto, don't even consider any ratio shorter than 4.88--

Should be 5.13 and if Ruby 5.38--there's no argument !

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ESP has a 6 speed in his jeep
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Old 03-20-2012, 05:43 PM   #15
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Thats funny, thats what he said !!


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ESP has a 6 speed in his jeep
What do you have in your jeep ??

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Old 03-20-2012, 05:43 PM   #16
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I think the 4.56 would work good for the Manual but saying that, I would go to the 4.88 because you can get Yukons in 4.88 but not in 4.56. And Yukons are just better. More for the fact that they are very quiet. there are several other good gear out their that carry 4.56 but they can be a little noisy like a M/T on the road noise

So it comes down to better gas mileage or better gears. But since your going to 35, I think you will be alright. As far as gas mileage is concerned, I would say you will get better mileage in the city with the 4.88 (under 55mph) but better gas mileage on the highway (over 60) with the 4.56. Most people see more city mileage for the most part

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