5.67 Gears?
JK Freak
Joined: Oct 2008
Posts: 896
Likes: 0
From: Colorado Springs, CO
You're thinking about it backwards. The problem is a too tall top gear on the highway, not a too tall low gear when on the trail. 5.38s are if anything already too low for trail use with a Rubicon and its 4:1 transfer case gearing. But they are still not low enough for correcting the too tall top gear when on the interstate. The fear would be of creating a "street only" Jeep, because by the time it was geared low enough for highway use, it may be geared too low for most trail situations.
JK Freak
Joined: Feb 2008
Posts: 632
Likes: 1
From: pensacola, florida
You're thinking about it backwards. The problem is a too tall top gear on the highway, not a too tall low gear when on the trail. 5.38s are if anything already too low for trail use with a Rubicon and its 4:1 transfer case gearing. But they are still not low enough for correcting the too tall top gear when on the interstate. The fear would be of creating a "street only" Jeep, because by the time it was geared low enough for highway use, it may be geared too low for most trail situations.
what I am getting at with a trail only Jeep, the lower the gearing equals higher rpm. meaning, if you gear too low, your rpm will be too high and you will not be able to achieve a higher speed thus becoming slower on the trail which many many people would love to do, slow down on trails, especially descending on hills
i can think of numerous people who have a rubi with 5.13 or 5.38 and would love to throw in an Atlas to slow down even more on the trails. i dont see at all how you think that 5.38 is too low for the trails on the JK. Now on some older jeeps that have a different engine with more power, yes, 5.38 is too low and they will run 4.10 or 4.56 and some of the rock crawlers will run 5.13
with the 5.67, i would be concerned with how high of rpm it is going to take you. if it is too low of gearing, you may never even hit 75 mph before your tach redlines. if you can not get enough speed before you turn high rpm, you will not be able to drive on the streets
sounds like u like your speed, maybe what u need is a different transmission along with gears and more power. so what it boils down to is like someone else stated, more power
JK Enthusiast
Joined: Apr 2010
Posts: 181
Likes: 0
From: Royse City, TX
so would that only really make a difference with an automatic?
JK Freak
Joined: Feb 2008
Posts: 632
Likes: 1
From: pensacola, florida
Not at all a concern. I mentioned on post one that 75 mph with 5.38 gears equals 2600 RPM. Redline is 5500 RPM, so with 5.38 gears you would have to be traveling 158 mph to hit redline in top gear. With 5.67 gears you are going to hit redline in top gear at 151 mph. Remember, this is the auto transmission JK we are talking about, with an overdrive ratio of 0.69:1
Sponsoring Manufacturer
Hypertech Representative
Hypertech Representative
Joined: Nov 2007
Posts: 357
Likes: 1
From: Bartlett, TN
Originally Posted by dlincoln91 
yep thats right. I had a meeting with hypertech last weekend and they talked about how gear ratio does NOT matter with any programmer its just an advertising point. The only thing that helps is the tire size change"
dlincoln91, its listed as a option because every vehicle minus the JK needs the value in the computer for the speedo and shift points to work correctly. The JK computer gets all this info from tire size alone.
"so would that only really make a difference with an automatic?"
The 6 spd jeeps require the tire size data for speedo info and the traction control system.
JK Jedi Master
Joined: Jan 2008
Posts: 11,463
Likes: 165
From: Austin <--> Colorado Springs
Higher speed dunes. I have seen several rubi guys that traded their 4:1 tcases straight-up for the x/sahara tcase. Don't recall if they were manual or auto, though.
I personally would love a rubi tcase in my auto for the lower offroad gearing, even though I have 5.38's in the axles. But there are those who feel it is too low "for their type of wheeling".
I personally would love a rubi tcase in my auto for the lower offroad gearing, even though I have 5.38's in the axles. But there are those who feel it is too low "for their type of wheeling".
Last edited by nthinuf; Feb 21, 2011 at 09:46 AM.
Super Moderator
Joined: Sep 2007
Posts: 1,750
Likes: 89
From: Arizona
I just reprogrammed my Jeep's computer with my AEV Procal module, and noticed that I could program it for 5.67 gears if I had them. Does anyone know if a company will be making 5.67 gears at some point for the JK? Strength issues aside, ... 5.38 gears don't seem to be quite low enough for an Unlimited with an auto trans and 37" tires.
JK Super Freak
Joined: Sep 2009
Posts: 1,527
Likes: 0
From: USA
Rubicrawler
Throw in an Atlas Rubicrawler and your problem may be solved, you get the added gear reduction when you want/need it and you get the option of doing it in 4 or 2 wheel drive. I have Pro Rock 60's with 5.38:1 gears, it's as tall (or low of gearing) as Dynatrac sells with the Pro Rocks so I would think that's all you can go for. Around town/hwy running 40"s, the 5.38's are fine, but on a few trails with steep sections, the stock trans and engine seem to be working harder than I would like them too. I'm going to do, at a minimum, the Rubicrawler addition or maybe just an Atlas T-case. If this isn't the route you like, you need to look at Ford 9" or a Corporate 14 bolt, for the taller than 5.38:1 selection. Currie Axles makes a Ford style 9" that is (I think????) compatible with the JK. The Corporate 14 bolt, well you are looking at custom builder territory there, but anything is doable.
Last edited by GCM 2; Feb 21, 2011 at 11:58 AM.