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Old 09-26-2012, 03:31 PM   #1
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Cool i need some assistance

Ok, so I have an 07 jk unlimited 4dr. No engine mods, stock gears, I have a 4" suspension lift, with 35" bfg mud tires. I need more power, torq, whatever.... Occasionally I tow a small camper under 2500lbs. Pulling hills is a pain and I feel the 3.8 v6 should have more then it does. What do I need? Please help! I've been looking at cat back systems, snorkels, engine computers, I have some money to spend but not sure what direction to go in first. I see Quadratec has a throttle response module ( supposed to make throttle response better) I see mpg boosters, I just don't know where to start to get more power, and or gas mileage, I understand I'm running 35's so mpg wont be to good but something has to give. Please help....

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Old 09-26-2012, 03:42 PM   #2
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Forget all the voodoo stuff...chips, exhaust, CAI.

One word: regear.

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Old 09-26-2012, 03:55 PM   #3
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You have an auto or manual transmission? Kbwwolf is right either way, but especially so if you have the auto. You need a regear.
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Old 09-26-2012, 04:27 PM   #4
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I have a manual trans. What gears should I go for and where do I get them.?
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Old 09-26-2012, 04:38 PM   #5
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Here is a link to another thread, this thread has a Gear Chart , check it out and it will show you what gears you need....."BH"

http://www.wranglerforum.com/f33/reg...-a-183033.html

Make sure when you look at the gear charts you look at the correct one....There is charts for the 3.8L and Charts for the 3.6L..... The 3.6L is different because of the difference in power curves and torque....
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Old 09-26-2012, 11:26 PM   #6
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Thanks for your help. I'm no expert, but from looking at the chart, I think I'm leaning towards 4.88's. Let me know if u think this is good. I don't plan on changing tire size, and I'm mote then likely not goin to be doin any heavy trailing. Mainly highway, and towing. Thanks again for all the help!
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Old 09-27-2012, 09:27 AM   #7
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Thanks for your help. I'm no expert, but from looking at the chart, I think I'm leaning towards 4.88's. Let me know if u think this is good. I don't plan on changing tire size, and I'm mote then likely not goin to be doin any heavy trailing. Mainly highway, and towing. Thanks again for all the help!
Yeah, for the 3.8 engine, with a manual transmission, and 35" tires, 4.88s are a popular choice. However, so are 4.56s.

Keep in mind that those charts are for ACTUAL tire size, not the size listed on the tire. So do yourself a favor and actually measure whether your tires really are 35s--most of the time 35s really measure about 34". If that's so, you may want to choose 4.56s.

Spend a little time on the highway holding off from shifting until you get to the RPMs the chart would put you in in 6th gear at 70 mph for your (actual) tire size. That'll probably be about 4th gear for you at some reasonable highway speed. I find that cruising on the highway between 2500 and 2800 RPMs is about right. Once I start creeping closer toward 3000 RPMs, the engine seems too loud to me and sounds like it's working hard, and I start really wanting to upshift.

Also consider how fast you like to drive on the highway. Are you more of a 65 mph guy, or an 85 mph guy?

You of course want to gear deeply enough so that 6th gear at whatever your preferred highway speed is produces a comfortable ride, knowing of course that you can always downshift to 5th if you need more power. (Keep in mind that 6th is supposed to be an "overdrive" gear for "crusing.") If you gear too deeply, then you run the risk that 6th gear on the highway at whatever speed you're comfortable with will put you into uncomfortably high RPMs for sustained cruising (for me, that'd be 3000+ RPMs), and you won't have any 7th gear to shift to.
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Old 09-27-2012, 09:31 AM   #8
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For a manual 07 and 35" tires go with 4.88. 4.56 are a waste for the 3.8L IMO.

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Old 09-27-2012, 09:39 AM   #9
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For a manual 07 and 35" tires go with 4.88. 4.56 are a waste for the 3.8L IMO.

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I dunno man . . . I've heard that a lot and must admit that I have not regeared my manual trans jeep, so I'm speculating here, but . . .

If 35s are really 34s, that means 6th gear at 70 mph is 2650 RPMs. That sounds about right for an overdrive. If you crept up to 75 mph, you'd be pushing 3000 RPMs with nowhere to shift to. With 4.88s, you'd be at 2840 RPMs at 70 mph--already just shy of 3000 RPMs.

Right now with my pathetic 3.21 gears and 33" tires, I've quit using 6th gear altogether. So I cruise in 5th, which at 70 mph is right about 2400 RPMs. I wish I had just a bit more juice at 70 mph . . . but not 3000 RPMs worth of it.

Close call IMO. Close enough that I think the "right" choice would vary depending on each driver's preference and overall highway time. Either way, he should definitly spend sometime on the highway paying attention to his RPMs and his speed, and seeing where he's most comfortable with an overdrive gear. JMHO.
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Old 09-27-2012, 09:54 AM   #10
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4.56 are ok if you never want to go bigger than 33's. I say its a waste cause most people once they start modifying their Jeep go to 33 then 35 with your 4.56 being no good for the new 35's. I got 5.13 in my auto trans and at 70 mph I am at about 2400 rpm, IMO a manual with 35's should be one numerically lower gear set, 4.88.

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Old 09-27-2012, 10:08 AM   #11
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4.88s without a doubt. if it was my rig i'd put in 513s. just me
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Old 09-27-2012, 10:11 AM   #12
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You want 4.88's at a minimum. 5.13's would make you happy when towing. Don't even consider 4.56 gears.
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Old 09-27-2012, 10:26 AM   #13
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RIPP makes a Nice Supercharger System
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Old 09-27-2012, 10:49 AM   #14
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Quote:
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You want 4.88's at a minimum. 5.13's would make you happy when towing. Don't even consider 4.56 gears.
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4.88s without a doubt. if it was my rig i'd put in 513s. just me
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For a manual 07 and 35" tires go with 4.88. 4.56 are a waste for the 3.8L IMO.
You guys are hardcore man.

I'll hold out my lone vote that he should at least consider 4.56s for the reasons I set out above. But no doubt 4.88s are the most common recommendation.
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Old 09-27-2012, 10:59 AM   #15
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I appreciate all the info and I'm leaning towards 4.88 but I'm goin to do some highway driving this wknd and do some calculations, now I'm thinking I'm between 4.88 and 5.13... I do like to drive between 70-80 on the highway when not towing. When I am towing, 5th and 6th gears are very difficult to hold cuz of slight hills on the highway, therefore I'm almost always stuck doin. Between 50-60 on the highway unless I downshift to 4th, but only when towing. And in 4th gear on the highway, I feel uncomfortable, as if I'm working the engine to hard. Large hills off the highway, I'm running 2nd 3rd gears goin up and again, I feel I'm working the jeep to hard, so let's say I change the gears. Then I need to keep the engine cool, should I go for heat reduction hood with snorkel, exhaust, supercharger?? Not sure what direction to go. This is my only vehicle and I drive it daily to work, then also haul camper on the wknds... Again any help is appreciated! Thanks
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Old 09-27-2012, 11:04 AM   #16
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How are 5.13's gonna work for me, for normal everyday driving on highway and on backroads? As far as torq, speed, power, and mpg. When not towing..?
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Old 09-27-2012, 11:05 AM   #17
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As opposed to 4.88's?
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Old 09-27-2012, 11:16 AM   #18
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Quote:
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How are 5.13's gonna work for me, for normal everyday driving on highway and on backroads? As far as torq, speed, power, and mpg. When not towing..?
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As opposed to 4.88's?
My expectation would be that it'd feel great down low. Leaving stop signs and the like, it'd feel very peppy. You'd probably row through the gears pretty quickly too, as RPMs would rise fast.

On the highway--assuming your tires are really 34"--I'd expect you'd be at just about exactly 3000 RPMs at 70 mph with 5.13s. That's too much for me, but for you maybe not. Get out on the highway or another open road and get going at a reasonable speed and stay in whatever gear gets you at about 3000 RPMs. Now imagine that's your RPMs on the highway when you're doing 70 mph during any trip or commute you may have, and there's nowhere to upshift to (i.e., there's no "7th gear"). That's what it'll be like.
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Old 09-27-2012, 11:25 AM   #19
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First off, you're making the incorrect assumption that more RPM's = hotter operating temperature. What you're not taking into account is the fact that the engine is working harder now than it will be when you've got the proper diff gear ratio installed. Right now, your engine has less leverage on the tires and the towing load due to the higher gear ratio. With 4.88/5.13's, the engine will have to work less because it will have more leverage thanks to the mechanical advantage provided by lower gears. Less work = less heat. So that's a non issue.

As for 4.88 vs. 5.13 when not towing, the difference is 5%.....not much. If 4.88's aren't too low, neither are 5.13's. You'll be sitting at around 2800 RPM @ 65mph with 5.13's vs.~1700 RPM now (assuming you have 3.21 gears). You say you drive in the 70-80mph range......trying to push a brick-shaped vehicle through the air at those speeds will have a more drastic effect on fuel mileage than running @ 3k RPM. Your 3.8 is perfectly happy at those RPM's and truthfully, at those speeds, it needs to be up there in order to efficiently move you. Lugging the engine is much worse than spinning a couple hundred extra RPM's.
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Old 09-27-2012, 01:44 PM   #20
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Ok, on my way home today, I payed attention to my speed and rpms, at 70mph in 5th I was running at approx. 2200rpm, at 70 in 6th I was running approx. 1800rpm. I'm not sure of the gears I have now, I know it is all factory. Thankyou for clearing up my confusion on the gears, I'm starting to understand now. To be honest, I know auto body, I'm not to knowledgeable on the mechanics of a vehicle, but Im willing to learn, so Thankyou for helping me along.
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Old 09-27-2012, 07:57 PM   #21
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5th is 1:1, 6th is .84. You have 3.21 gears like I suspected. You'll be in love with proper gears.
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Old 09-27-2012, 08:20 PM   #22
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So ur thinking I'd be better off with 4.88's or 5.13's ? Will either one of those help me also if I decide to do some wheeling, I'm guessing from what I gathered so far, my low end torq will be great also... ? Cuz it sucks now, I tried doin some wheeling and I've gotta burn the hell out of the clutch to get it to climb. Hence, I don't wheel as often as I have in my older jeeps, in the past.
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Old 09-28-2012, 07:04 AM   #23
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Your crawl ratio right now is 4.46 (NSG370 first gear) x 3.21 (diff ratio) x 2.72 (NP231 low range ratio) = 39:1

It will increase to almost 60:1 with 4.88 gears and a bit over 62:1 with 5.13 gears. With 4.88 gears you'll crawl 54% slower than you do now....I can tell you from experience that in 4 low, you won't (and shouldn't) ever touch the clutch unless you're coming to a complete stop. It will take you a while to break the habit and realize how little you actually need to touch the clutch. A good driver will look like he's driving an auto with a properly geared manual-equipped rig.

You're gonna be spinning significantly higher RPM's at highway speed whichever way you go. 5.13's will set you up for 37's if you plan to go that route in the future and will make towing very nice. 4.88's will be no slouch at all and would work fine for you.
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Old 09-28-2012, 01:23 PM   #24
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Another question, when ordering my 4.88 gears from Quadratec, it says for a Dana 44 rear axle? Is that what I have? Stock? I do not have a Rubicon. I thought the Dana 44 only came stock on Rubicons. If that's not what I have, what would I have and what or how do I order the gears. My jeep is however a Sahara. Also looking to buy an exhaust system. Looking at borla cat back system, any reviews or suggestions on this product?
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Old 09-28-2012, 01:24 PM   #25
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Also as far as the gears go, do I need the same front and rear? Or just replace the rear?
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Old 09-28-2012, 02:39 PM   #26
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Another question, when ordering my 4.88 gears from Quadratec, it says for a Dana 44 rear axle? Is that what I have? Stock? I do not have a Rubicon. I thought the Dana 44 only came stock on Rubicons. If that's not what I have, what would I have and what or how do I order the gears. My jeep is however a Sahara.
In general, all JKs come with D44 rears and D30 fronts.

However, in 2007, you were able to order an "offroad package" on the Sport that gave you D44 fronts and rears, I believe. Not sure if that was available on the Sahara. To further complicate matters, a handful of early 2007 JKs came with the old D35 rear axle.

So it's hard to know just what you've got without knowing more than merely it's a 2007 Sahara. If you register your VIN on jeep's website, you should be able to download your build sheet and confirm your axles.

Also, I would use Q-tec and the like to price various gear sets, but I wouldn't order them. You're going to need a shop to do this work (it's complicated), and the usual advice is to let the shop order the gears they recommend (provided they give you a fair price) so that the shop can't weasel out of any warranty issues by asserting that YOU ordered crappy gears.

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Also as far as the gears go, do I need the same front and rear? Or just replace the rear?
Unless you want to remove your front driveshaft and become a 2x4 jeep, you need to do front and rear.

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Also looking to buy an exhaust system. Looking at borla cat back system, any reviews or suggestions on this product?
Opinions vary, but I say save your money. Unless you're really going to do front to back with the "air" mods--new intake, new throttle body, new headers, highflow exhaust from the headers on down--they don't do much (if anything) for jeeps.
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Old 09-29-2012, 08:48 AM   #27
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Unless you're setting up the gears yourself, and I doubt you are, have the shop doing the work purchase them.
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Old 09-29-2012, 11:50 AM   #28
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Very helpful info. Thankyou! I called a shop And set up a time for them to do it, they r saying they will have jeep for approx. 3days and an estimated price for the project is around 1700.00 is this about right for the project give or take a few hundred. Also, I will hold off on any exhaust mods for now, until I can do the whole thing front to back, again thanks for all your help.
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Old 09-29-2012, 12:01 PM   #29
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Ok, my birthday was yesterday and my girlfriend got me a "G-Force" computer chip specifically for the 07 wrangler. It looks to be an easy install, only two wires. I don't know anything about this product. Anybody have any info on this product. Likes, dislikes?
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Old 09-29-2012, 12:25 PM   #30
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Very helpful info. Thankyou! I called a shop And set up a time for them to do it, they r saying they will have jeep for approx. 3days and an estimated price for the project is around 1700.00 is this about right for the project give or take a few hundred. Also, I will hold off on any exhaust mods for now, until I can do the whole thing front to back, again thanks for all your help.
Anywhere from $1200 to $1700 is fairly typical. Ask if they'll do it for $1400 and compromise from there.

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Ok, my birthday was yesterday and my girlfriend got me a "G-Force" computer chip specifically for the 07 wrangler. It looks to be an easy install, only two wires. I don't know anything about this product. Anybody have any info on this product. Likes, dislikes?
Snake oil.

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