5.13 gears
JK Super Freak
Joined: Apr 2007
Posts: 1,258
Likes: 1
From: Prosper, TX
Here is that JKU in Moab.
http://www.youtube.com/watch?v=UTT9b...tbQgkEb4Je08sC
So, been there, done that, got the t-shirt. Listened to y'all screaming constantly about lower gears and it was a mistake.
JK Super Freak
Joined: Apr 2007
Posts: 1,258
Likes: 1
From: Prosper, TX
All I can say is; Wow.
I guess if you live in Texas, the JK is geared perfectly from the factory. For the rest of us, re-gear, you won't be sorry. Heck, I re-geared to 5.38 with stock tires, a little low, but I liked it.
Oh, and if you can't post from your Iphone, get an Android.
I guess if you live in Texas, the JK is geared perfectly from the factory. For the rest of us, re-gear, you won't be sorry. Heck, I re-geared to 5.38 with stock tires, a little low, but I liked it.
Oh, and if you can't post from your Iphone, get an Android.
Can post from iphone, just didn't want to type that much on it.
JK Super Freak
Joined: Apr 2007
Posts: 1,258
Likes: 1
From: Prosper, TX
The only regrets I have read from automatic owners are from people who didn't gear low enough (I.e. 4.88s instead of 5.13s, or 5.13s instead of 5.38s), with CJ7nvrstk as the only exception. Although, he did not try 5.38s with his 37s for a basis of comparison.
I have occasionally read posts of people who did 5.13s with a 6 speed and 35s who daily commute at speeds over 75 mph who felt they went too low. They typically just drive a little slower or upgrade to 37s.
I have occasionally read posts of people who did 5.13s with a 6 speed and 35s who daily commute at speeds over 75 mph who felt they went too low. They typically just drive a little slower or upgrade to 37s.
JK Super Freak
Joined: Apr 2007
Posts: 1,258
Likes: 1
From: Prosper, TX
For a 2 dr (lighter than a 4 door) with a 6 speed on 35s, at close to sea level in a relatively flat area, with daily travel at 75+ mph, I would agree that 4.56s would be more suitable than 4.88s.
This is kind of a unique situation though. There are more 4 dr JKs than 2 dr JKs. Those who live far enough West to travel at 75+ mph often live close to mountains (California, the Rocky Mountain States, etc.).
Nonetheless, yours is a good example of the exception.
This is kind of a unique situation though. There are more 4 dr JKs than 2 dr JKs. Those who live far enough West to travel at 75+ mph often live close to mountains (California, the Rocky Mountain States, etc.).
Nonetheless, yours is a good example of the exception.
BTW, he is at 3800 ft or so. With hills.
JK Junkie
Joined: Jul 2008
Posts: 3,017
Likes: 0
From: Lakewood, OH
To start off with I have a 11 2dr 6speed
Not trying to start another argument or anything but Like i have been telling people and everyone here probably already knows where i stand on this whole situation 4.88s with 35's is way to much still traveling at 75+mph. if you have a manual and do a lot of highway and don't ever plan on going to 37's go with 4.56s. I can run 37s on my 4.88s with no problems even going up the big mountain we have here in the middle of the town. i get my best mpg going about 60-62mph if i go any higher it drops tremendously. This is my opinion just as everyone else has theirs im just trying to give you my situation so you or anyone can learn from it. i will add the 4.88s are great power around town but highway it makes me regret ever getting them.
Not trying to start another argument or anything but Like i have been telling people and everyone here probably already knows where i stand on this whole situation 4.88s with 35's is way to much still traveling at 75+mph. if you have a manual and do a lot of highway and don't ever plan on going to 37's go with 4.56s. I can run 37s on my 4.88s with no problems even going up the big mountain we have here in the middle of the town. i get my best mpg going about 60-62mph if i go any higher it drops tremendously. This is my opinion just as everyone else has theirs im just trying to give you my situation so you or anyone can learn from it. i will add the 4.88s are great power around town but highway it makes me regret ever getting them.
In other words, if the right gear set at 70mph is 4.88s it's going to be the same at 75mph.
One thing I think people get confused over is that a 5% numerically higher gear set is going to eat 5% more fuel at the same speed. The primary difference isn't the amount of power that is actually getting put to the rear wheels, but rather less power per stroke, more manifold vacuum and the throttle blade closed a little more. Sure there is some extra parasitic loss of power with friction and spinning accessories, but it won't be the 5% the additional rpm represents.
so if you flip this around the other way, and not going to drive over 60mph, 4.56s would make a lot more sense than 4.88s.
JK Junkie
Joined: Jul 2008
Posts: 3,017
Likes: 0
From: Lakewood, OH
You are right Jpop, torque is like the hammer. It is what does the work. It does the pulling to maintain that speed. Why are torque figures so important to the truck cowd in their 1 ton trucks? Because it's that torque that does the work of pulling that trailer, not HP.
And yes, lifting and bigger tires increaess drag but it is the torque that takes care of that, not the HP. You are using the wrong unit of measurement in your calculations.
As for personal experiences, I guess I have been blessed with big block like torque in my 2 JKUs then because even today cruising at 1600 rpm on the freeway my JKU did not down shift out of overdrive up a extended grade. Now I'm not saying it never does, but it does not do the gear hunting that so many here want to claim.
So again, 8 out of 10 Jks coming out of the factory are geared to run the 1900-2200 rpm range. Why? Because it simply works.
And yes, lifting and bigger tires increaess drag but it is the torque that takes care of that, not the HP. You are using the wrong unit of measurement in your calculations.
As for personal experiences, I guess I have been blessed with big block like torque in my 2 JKUs then because even today cruising at 1600 rpm on the freeway my JKU did not down shift out of overdrive up a extended grade. Now I'm not saying it never does, but it does not do the gear hunting that so many here want to claim.
So again, 8 out of 10 Jks coming out of the factory are geared to run the 1900-2200 rpm range. Why? Because it simply works.
Torque has no measurement for the frequency it is delivered.
JK Enthusiast
Joined: Nov 2010
Posts: 174
Likes: 0
From: Fort Collins, Colorado
Had an 08 JKU that was totaled in an accident in OCT. It was set up with a Hypertech tuner, Viper TB, K&N air cleaner, and 5.13 gears pulling 37s. And it was overgeared because I read the threads on here instead of flollowing my instincts. My instincts said 4.88s and I should have listened to em. My hiwhay mileage went from 17 MPG to 15.5 MPG. If you really did read what I posted you would see where I have stated that but it seems like some on here just want to beat their drum longer and harder to try to convince everyone of their superiority. So again, I listened to those on here that said 5.13s and it was a mistake. I got better highway mileage with 3.73s and those same 37s. Why? Because I wasn't over revving the motor because there was enough torque to maintain 70 and still get 17 MPG. So, "correctly geared" as you put it was in actuality overgeared.
Here is that JKU in Moab.
http://www.youtube.com/watch?v=UTT9b...tbQgkEb4Je08sC
So, been there, done that, got the t-shirt. Listened to y'all screaming constantly about lower gears and it was a mistake.
Here is that JKU in Moab.
http://www.youtube.com/watch?v=UTT9b...tbQgkEb4Je08sC
So, been there, done that, got the t-shirt. Listened to y'all screaming constantly about lower gears and it was a mistake.
JK Freak
Joined: Sep 2010
Posts: 696
Likes: 0
From: Syracuse, NY
For a 2 dr (lighter than a 4 door) with a 6 speed on 35s, at close to sea level in a relatively flat area, with daily travel at 75+ mph, I would agree that 4.56s would be more suitable than 4.88s.
This is kind of a unique situation though. There are more 4 dr JKs than 2 dr JKs. Those who live far enough West to travel at 75+ mph often live close to mountains (California, the Rocky Mountain States, etc.).
Nonetheless, yours is a good example of the exception.
This is kind of a unique situation though. There are more 4 dr JKs than 2 dr JKs. Those who live far enough West to travel at 75+ mph often live close to mountains (California, the Rocky Mountain States, etc.).
Nonetheless, yours is a good example of the exception.
I'm also a 2dr 6 spd going to 37s someday. 4.88 would be best? Mixed city highway DD. Rare rocks off road, mostly mud around me.
JK Freak
Joined: Sep 2010
Posts: 696
Likes: 0
From: Syracuse, NY
Assuming you don't run ubber heavy 37s:
If your highway travel is routinely over 75 mph, you'd want 4.88s with 37s and your 2 dr 6 spd.
If your highway travel is usually at 65 mph, you'd want 5.13s.
In between, it depends on whether you prioritize power or economy. Although, if you prioritize economy, you likely wouldn't run 37s.
I love 5.13s with a 6 speed and 37s because most of my miles are 70 mph and under. When I travel 75+ mph, I am driving through the steep freeway grades of Montana, and power is more important to me than fuel economy. If or when fuel economy is more important, I just slow down. At 60 mph, I can get 20+ mpg with 5.13s and 37s with a 6 spd if it is not too windy.
If your highway travel is routinely over 75 mph, you'd want 4.88s with 37s and your 2 dr 6 spd.
If your highway travel is usually at 65 mph, you'd want 5.13s.
In between, it depends on whether you prioritize power or economy. Although, if you prioritize economy, you likely wouldn't run 37s.
I love 5.13s with a 6 speed and 37s because most of my miles are 70 mph and under. When I travel 75+ mph, I am driving through the steep freeway grades of Montana, and power is more important to me than fuel economy. If or when fuel economy is more important, I just slow down. At 60 mph, I can get 20+ mpg with 5.13s and 37s with a 6 spd if it is not too windy.
My highway speed is 65ish
My in between I would prefer economy... which would be best with 4.88 or 5.13? (I know economy is a relative term in the 37 world.)
Still confused.
JK Super Freak
Joined: Apr 2007
Posts: 1,258
Likes: 1
From: Prosper, TX
Not once!
Properly geared is what I aim for, not overgeared.
My CJ is a deicated trail rig running those 4.88s. By crunching the numbers, I determined that 4.88s would be the ideal gears for that set up to allow me to be competitive in the sand drag racing I was doing with it but still allow me to rock crawl as well. When I chose those gears, highway RPM was not an issue since it doesn't see significant highway time. Only to and from the desert and the drag strip. No long road trips like in the JK where those extra several hundred rpm will kill your mileage big time over a 1200 mile trip. So think about it. 1200 miles at 75 is 16 hrs driving time. 16 hrs is 960 minutes, which then turns into 288,000 extra revolutions my motor is taking that it really doesn't need to take.