5.13 gears
JK Junkie
Joined: Jul 2008
Posts: 3,017
Likes: 0
From: Lakewood, OH
I certainly don't mind seeking me out for help, just keep in mind you should weigh my answers with your own experiences and the advice of others. I'm pretty sure that's why we're all here.
JK Junkie
Joined: Jul 2008
Posts: 3,017
Likes: 0
From: Lakewood, OH
My parents had a Town and Country with the same engine our JK's have. When I was considering a regear, I did some observations on it's highway performance. It seems that it ran similar RPM's as our JK's do at the same speeds. That is to say that at 70, both would turn around 2000 RPM's. However, the Town and Country almost never had to downshift. It cruised right along at 2000 RPM's on the highway without an issue. Perhaps the gearing in the JK's is appropriate for the engine, but not the aerodynamics. On paper, it should have been perfect, but in application, especially after a lift and new tires, it was downright aweful.
IIRC, the new 2012 auto's are geared lower in the transmission, and have a higher output engine. If nothing was wrong before, why lower the ratio after adding the Pentastar? My parents just got a new Pentastar powered Caravan (equivelent to the Town and Country) and it's RPM levels are the same as with their old T&C. I think this showes that Jeep did see an issue with the old 07-11 JK driveline configuration, and took steps to correct it.
IIRC, the new 2012 auto's are geared lower in the transmission, and have a higher output engine. If nothing was wrong before, why lower the ratio after adding the Pentastar? My parents just got a new Pentastar powered Caravan (equivelent to the Town and Country) and it's RPM levels are the same as with their old T&C. I think this showes that Jeep did see an issue with the old 07-11 JK driveline configuration, and took steps to correct it.
Not sure by any means, but quite possibly the Pentastar was scheduled to be released at the introduction of the new JK. Enter Daimler to get in the way and trying to sell off this albatross and leveraging the brand to create new sales. What I see in the 2012 JK is everything I had hoped my 2007 would be. Perhaps, just perhaps that is exactly what the engineers had hoped it would be as well.
JK Newbie
Joined: Oct 2011
Posts: 37
Likes: 0
From: Fort Worth, Texas
Well planman, I have a '11 sport S 4 door JK and driving around the Fort Worth area feels like my jeep is lacking power/balls. I can't imagine not regearing all Jeeps. I have been putting my build list together and one of the 1st things i have on my list is new gears. So far that is the only complaint i have had with my JK. I'll let you know how it feels when i get my regear done.
JK Enthusiast
Joined: Nov 2010
Posts: 174
Likes: 0
From: Fort Collins, Colorado
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.
JK Junkie
Joined: Nov 2010
Posts: 2,261
Likes: 0
From: Whitefish,Montana
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.
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JK Newbie
Joined: Apr 2010
Posts: 1
Likes: 0
From: Colorado Springs, CO
If you have an automatic transmission that hunts between the overdrive and 3rd gear at highway speeds with your stock gears now, you will notice an improvement in fuel economy with 5.13s.
This is plain logic because when an automatic transmission downshifts at close to wide-open-throttle with frequency, the fuel economy is much worse than running slightly higher rpms in the overdrive gear with minimal downshifting.
That being said, 5.13s in an automatic 07-11 JK are completely worth it for 33"-35" tires just for the improved performance alone--irrespective of the improved mpg.
This is plain logic because when an automatic transmission downshifts at close to wide-open-throttle with frequency, the fuel economy is much worse than running slightly higher rpms in the overdrive gear with minimal downshifting.
That being said, 5.13s in an automatic 07-11 JK are completely worth it for 33"-35" tires just for the improved performance alone--irrespective of the improved mpg.
JK Newbie
Joined: Oct 2011
Posts: 37
Likes: 0
From: Fort Worth, Texas
This may seems like a stupid question but i was wondering what the difference was between the 4.88 reverse and the regular 4.88's? I am certain i will need to regear and since i know exactly sqwat about gearing i don't know what to order. When i look them up they always ask for reg. or reverse. Will i need to by gears for both?
Please help the blind....
Thank you.
Please help the blind....
Thank you.
JK Freak
Joined: Jan 2011
Posts: 933
Likes: 0
From: El Paso, TX
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.