New JK / MPG & Lift Question - JeepForum.com

 
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post #1 of 8 Old 08-08-2010, 07:31 PM Thread Starter
aermotor
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2007 JK Wrangler 
 
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New JK / MPG & Lift Question

Hey everyone! Picked up a used 2007 JK Sahara Unlimited last week and boy do I love it! It's got (I believe) a Rough Country 6" X-Series lift. I just put new 35" BFG KM2s on her as well. Few questions if I may from you experienced JK guys/gals!



MPG / Performance
I've been reading a lot of posts about the Superchips Flashpaq etc. on improving performance and mpg. Below is what my JK is running with and without OD.

OD OFF
70mph @ 2850rpm in 4th gear

OD ON
70mph @ 2000rpm in 3rd gear (downshifts constantly)

I've read A LOT of people have problems with the tranny shifting up and down all the time when hitting the slightest of inclines with OD ON and I'm having the same issue. So I tried turning OD OFF and you can see what my RPMs are above. It's more more stable and I don't get the constant up and down shifting, but I need to know am I running too high rpm to be getting decent milage, or is that a god range? Do you know what gearing I might have? I'm thinking it's 4.10 but feel it might not be stock.

I don't think I'm getting the correct odometer/mpg readings either because of the 35" tires, I don't think the original owner get it re-calibrated but I can't tell....


Rough Country Lift
I think I have the 4" or 6" X-Series lift but really am not sure and there's no information from the dealer on any of the aftermarket stuff. Can anyone tell by the pics if it's the X-Series or regular? This lift is pretty gigantic so I'm wondering if I can adjust it if it's the X.

Front


Rear


Front


Front


Rear


Anyway, thanks in advance for any help! Just trying to figure out more about what I have hear. I love this beast. Just need to get it tuned to run better.

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post #2 of 8 Old 08-08-2010, 08:29 PM
McKBrew
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Not sure what type of lift it is by looking at it, but size wise I am going to guess 4" just by where the tires are sitting in the fenderwells.

Not sure about the gears, but you could contact Chrysler for a build sheet and see what was installed. Another way to tell especially if they are aftermarket gears is by doing what is detailed in this thread.
http://www.jeepforum.com/forum/f96/w...7/#post9832965

The answers to some of your other questions might be here.
http://www.jeepforum.com/forum/f96/j...reads-1074059/
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post #3 of 8 Old 08-09-2010, 05:18 PM Thread Starter
aermotor
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I looked through most of that and didn't find many answers to my specifics of 3rd gear vs. 4th gear. Not sure if running 2900 in 4th instead of 2000 in 3rd is better for milage.
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post #4 of 8 Old 08-09-2010, 09:06 PM
RockyClymer
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I noticed that it appears the vent tube to your rear differential/axle is hanging down in the last picture you posted...needs to be relocated higher up with the original clip. (It is that rubber tube with the white plastic tip in it).

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post #5 of 8 Old 08-09-2010, 09:18 PM Thread Starter
aermotor
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Ahh yes thank you! I saw that too and wondered what it was, dealer (Chevy) had no clue, bah! It looks like it's snapped off so I'll take a look. It's under Aut Nation warranty and I found some other stuff wrong with it, so if I can't just plug it back in I'll have them fix that.
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post #6 of 8 Old 08-10-2010, 01:09 AM
asknight
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The Superchips will definitely help to some extent in that it will move the trans shift points to where they should be for your tire size, while also correcting your speedometer and odometer, resulting in your dash calculated fuel economy being more accurate.

However, for you to get back to close to stock performance levels with that lift and tires, 5.13 gears are required.
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post #7 of 8 Old 08-10-2010, 08:17 AM
Blu-Jacket
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If you're not sure about the speedo being accurate, might try comparing it with a portable GPS. If you need to correct it, the AEV Procal and Superchips will do the job.
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post #8 of 8 Old 08-10-2010, 08:31 AM
JIMBOX
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These guys have it pretty well tagged for your problems and I've looked at this several times--just noticed that--

The brake lines appear to be streched, at "REST", whick means that your first real "Flex"could be areal problem and

The rear brake lines, besides being streched to far, are rubbing against the swaybar and thats DISASTER, along with the strech !!

checkitout !!

Good luck

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