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Finally had enough of the completely sluggish performance of my 09 sahara 4 door. Made a call to Northridge 4x4 and order 5.13 Yukon gears with the master bearing kit. Had a good mechanic I know install them today. I have read a ton of threads about the difference that gears make and thought i would help those out who are on the fence with the cost.

First impression. Got in and drove home from shop. Tranny is shifting quickly but man it just feels like I am getting all of the power that the anemic 3.8 has available. It is somewhat effortless to get up to speed. The drive home brings a smile to my face.
I hook my Superchips flashcal and tune CPU for correct gears and then take for a test drive. Now I get it. It is back to stock or better performance. I have a AFE intake with Flowmaster exhaust. It is night and day on acceleration. granted its still a lifted jeep (3.75") but it feels so much more responsive. when pulling out into traffic I no longer feel like I am having to hold my foot to the floor to pace traffic. I cant wait to see the difference off road. I am on the fence with upgrading to the flashpaq and selling the flashcal. Its hard to justify the cost. For those that wonder if the cost of gears are worth it, my simple answer to you is yes. If you want to enjoy driving your lifted jeep with larger tires, beg and borrow to get it done. I have 33's now but will upgrade to 35s when these are done unless I can find someone who wants to swap.
 

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X2 on my 2012. Pulled my M101a2 loaded with my dauter's college move-in stuff from Livermore to Reno this weekend and was really glad I had the 5.13s. Set it on cruise and let it walk. Very few down-shifts to 3rd, even in the sierras. Gears are kinda like the Curtis-Mathis TV slogan from back in the '60s and '70s: "a little more expensive, but darn well worth it."
 

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I went with 5.38s a couple weeks ago. 2010, 4 door, automatic, 35s. Other than not being able to get out of it's own way, 4:10s and OD off drove better to me around town. Now with OD off, the RPMs are too high for around town, and with OD on, 4th gear feels like it's lugging the engine. MPG stayed about the same, don't know freeway MPG yet. My exhaust (Dynomax Evo Comp) drones like crazy now because of the RPM range (30-40 MPH, 1500 RPM) I stay in around town. Only benefit I feel like I got was being able to use OD on the freeway.

I'm using a ProCal, but I've also been thinking of switching to a Flashpaq.
 

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I am running 295/70/R18's and looking forward to regearing. I think I will be going with 4.56. I have a shop lined up to do it just need the time to get done. Glad to hear you are happy with your results.
 

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I've been satisfied with the 5.13's in my 2010 4dr auto. My gas mileage is about the same as it was before, but the before was also without any lift and 32" tires. Obviously the tires added weight, as did the addition of more armor, tire carrier, etc. The lift increased the frontal area so wind resistance went up. All that considered my mileage is relatively good - 15.5 in town and about 1mpg more on highway.

Where I really noticed the difference was last weekend on the highway and off road. I was able to get up to speed quickly without having to floor it. With cruise control set at 75 mph I was maintaining speed even going up some of the steeper Colorado grades without having to turn off the OD or seeing the engine rev to 5K + as it used to. Climbing obstacles off-road also seemed very easy as compared to before when it had 4.10 gearing.

Everyone complains about the 3.8L engine's power, especially when they like to compare it to the output of the previous generations 4.0 I6. The problem with the 3.8's output, which is higher than the 4.0 I6, is where it makes that power in the high end. Mainly the problem was that the factory didn't match the gearing very well to the engine. They kept their costs down by sharing an engine across platforms, but given the criticism of the engine that it drew in the wrangler, it may have cost them as much in sales or such as what they saved in manufacturing.
 

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Driving it around town is nice... but wait untill you try it on the trail! Our first wheeling trip with the 5.13's was in Clayton, OK and the ability to crawl up or down ANYTHING without touching the gas or brakes.
 
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