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Unread 09-05-2012, 11:09 PM   #16
12Htownsahara
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2012 JK Wrangler 
 
Join Date: Jul 2012
Location: Magnolia, Tx
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With that being said 5.13s would work fine for me even though my driving is mostly hwy? I often drive mine between 75-80 mph and I feel safe doing it. The jeep seems plenty stable even with my 35s and lift. Overall I just don't want to "overgear" myself in an attempt to gain a few Mpgs. I'm getting 15-16 now but would love to see some 18s or so.

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Unread 09-06-2012, 05:33 AM   #17
gwar11d2
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In a 2012 wrangler with automatic and the 3.6L Pentastar motor, 5:13's are going to be too low of a gear (numerically higher) and you'll be running 3000+ RPMs on the highway with 35" tires.

Another source from the FAQ: http://www.jeepforum.com/forum/f96/s...lator-1298121/ Which shows you engine rpm, speed and in which gear. Overdrive numbers (highway) are on the bottom row.

You can download an excel chart and play with the numbers. I still say 4:1 or 4:56 to keep your motor in a good efficient range for both power and best MPG.

Keep in mind, you're driving a brick on wheels. I would say 16MPG is fairly decent given you already have 35's. Best way to increase that is to take your 75-80MPH and drop it to 65-70MPH and enjoy the ride
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Unread 09-06-2012, 01:41 PM   #18
Existence
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I have just had 4:88's installed on my 3.6 with 37's. I could not find any definitive information on ratios for the 3.6's only speculation so I took a chance.

After driving it for a few hundred miles I would run 4:88's with 35's and jump to 5:13's for 37's. Although one would have to take our altitude into consideration, 6000ft above sea level sucks power.

At 75Mph I am sitting at just over 3000rpm (Yes, that is our legal speed limit on freeways ) which is under stock if I remember correctly.
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Unread 09-06-2012, 04:04 PM   #19
jwmbishop
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The way my 12 Sport Auto feels 5.13 would be overkill on 35s with it - pure genocide with the stick! And I love gears!
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Unread 09-06-2012, 07:34 PM   #20
Butterbuddha
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You really need to listen to your fellow '12 drivers. Its a whole different ballgame with the rest of us. I don't regret my 5.13s, but my 2 door is ungodly heavy and I have the 3.8. I would think your 80+ more horsepower would lead you to 4.88s or so. (Though in my case I still bounce between 14 and 16mpg. But I am geared for power not top end)

5.13s for you seem suited for bigger, heavier tires than you plan on running. But once again, refer to my first sentence.
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