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Discussion Starter · #1 ·
Hello,

I'm the latest FNG. See here: http://www.wranglerforum.com/f12/new-from-tx-with-a-fastback-jku-254416.html

So, I've got tons of questions and am mad searching this forum but am slightly overwhelmed. I'm going to have to level or lift because my tires rub. It is also a slug with terrible gas mileage so I'm guessing the answer is new rear end gearing. Are the reprogrammers any help (e.g. FlashCal)? I need to figure out bumpers and side steps or ??? Any patient help appreciated from someone who has been through this with a 2011.

Thanks,
Kevin Williams
 

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If you plan on ever using your 4wd you will need to regear the front also.
 

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I think I saw your rig in the welcome forum. You said something about tire rub??? Your tires are a bit big for runnin stock. Couple issues you may have:

Improper backspace on rims(those aint stock)
Tires to big to run without lift(looks like you need about 2.5"/ Body lift wont do)

Your options:
New rims with more backspace
2.5" lift
Both
3/4" spacers(some people don't like them but I ran them for years)

Its a nice rig tho, that was all just thoughts, without lookin at it up close its hard to tell.
Find a 4X4 shop and hang around. You will be shocked how much you will pick up. And of course all of us are here.
 

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If you plan on ever using your 4wd you will need to regear the front also.
YEA, that. You have to regear both axles when you do it chief. 4x4 world cost double for everything.
 

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Btw, I do have a build thread on another forum for my 2011. PM me if you want the link.
 

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Hello,

I'm the latest FNG. See here: http://www.wranglerforum.com/f12/new-from-tx-with-a-fastback-jku-254416.html

So, I've got tons of questions and am mad searching this forum but am slightly overwhelmed. I'm going to have to level or lift because my tires rub. It is also a slug with terrible gas mileage so I'm guessing the answer is new rear end gearing. Are the reprogrammers any help (e.g. FlashCal)? I need to figure out bumpers and side steps or ??? Any patient help appreciated from someone who has been through this with a 2011.

Thanks,
Kevin Williams
I've never used a programmer but my opinion is that your money would be better spent getting your gearing dialed in for whatever tires you plan to run. Once this is done you'll have a better idea of what, if any, power mods you'll need/want to make.

Here is a website you can use to play with some gearing numbers:

Gear Ratio Calculator (This site allows you to put two sets of numbers in so that you can do a side by side comparison.)

The information you will need for the above site:

Step 1. Transmission

Automatic trans ratios: (1) 2.84, (2) 1.57, (3) 1.00, (4) 0.69, and (R) 2.21.

or

Manual trans ratios: (1) 4.46, (2) 2.61, (3) 1.72, (4) 1.25, (5) 1.00, (6) 0.84 and (R) 4.06

Step 2. Transfer case

X/Sport/Sahara: NV241, 2.72:1 low range (listed on the site as NP241/NV241/NVG241)

or

Rubicon: NVG241OR, 4:1 low range

Step 3. You probably don't have this.

Step 4. Some common ratios are: 3.21, 3.73, 4.10, 4.88, 5.13

Step 5. Pretty much self explanatory.


And a convenient tire size converter: DML Tire and Wheel Calculator


Some basic mechanical information (depending on what you've got):

Automatic transmission is Dodge's 42RLE four speed. The main problem I've read/heard about with this transmission and larger tires against stock axle gearing is that it is constantly searching for the right gear at highway speed and is a dog when trying to pass. A programmer will help with this since it allows you to adjust shift points.

Manual transmission is the Daimler/Chrysler NSG370. I believe there were a couple of technical service bullitens (TSB) on these for correcting an issue of popping out of gear in 1st or 2nd (should be able to check your Jeeps history to see if any fixes were performed). Otherwise it is a good transmission and is still used today.

Axles:

X/Sport/Sahara front: Dana 30 with 3.21 or 3.73 gears (4.10 optional towing package in 07, 08 forward only 3.73 is optional).

X/Sport/Sahara rear: Dana 35 with 3.21 or 3.73 gears (4.10 optional towing package in 07, 08 forward only 3.73 is optional).

Rubicon: Dana 44 with 4.10 gears.

Just some axle basics: Project-JK.com - Jeep JK Wrangler Resource » Jeep JK Wrangler Axle Basics

There are also a couple of of other pages that GrimmJeeper has done that are pretty informative:

Differentials
Regearing Basics


This site has a variety of write-ups for various model year JK's: Project-JK.com - Jeep JK Wrangler Resource » Jeep JK Wrangler Axle Basics

This one has the same information as the one above but also has some user write-ups: WRITE-UP INDEX: The Quintessential Source for Do it Yourself Write-Ups


Welcome to Jeeping and thr forum!:wavey:
 

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Here's some more information that I posted in another thread, some of it is a repetition of the above.

Welcome to Wranglers and the forum!

A couple of things off the bat.

The 07-11 JK's run the 3.8 V6 with either a 6 speed manual or 4 speed automatic transmission.

The 12 and newer JK's run the 3.6 V6 with the same 6 speed manual or the newer and better 5 speed automatic.

*****What follows is only what I have read about and/or heard from others as I jumped from stock 32 inch tires with 4.10 gears to 37 inch tires with 5.13 gears (09 JKU manual trans BTW)*****

The 3.8 with the manual is not too bad with 35 inch tires and can be run with 3.73 gears (good) or 4.10 gears (best).

The 3.8 with the auto is notorious for being difficult to fine tune for all around driveability with 35 inch tires and either 3.73 or 4.10 gears as the gear ratios in the transmission are spread too apart to maintain the programmed parameters in the stock configuration of the PCM and the transmission is almost constantly searching for the right gear to maintain speed.

The 3.6 with the manual is even better than the 3.8 with 3.73 or 4.10 gears.

The 3.6 with the auto approaches (if not equals) the manual in all around driveability with 3.73 or 4.10 gears.

With all that said, on with the information site!

This site can be used to play with some numbers and allows you to compare two different setups side by side (check stock against theoretical).

Gear Ratio Calculator

Use this information to plug into the above site:

Gear ratios for the NSG370 (6 manual) are: (1) 4.46, (2) 2.61, (3) 1.72, (4) 1.25, (5) 1.00, (6) 0.84 and (R) 4.06.

Gear ratios for the 42RLE (4 auto) are: (1) 2.84, (2) 1.57, (3) 1.00, (4) 0.69, and (R) 2.21.

Gear ratios for the W5A580 (5 auto) are: (1) 3.59, (2) 2.19, (3) 1.41, (4) 1.00, (5) 0.83, and (R) 3.16.

To determine what gear ratio you currently have (in case you don't know), you can contact Jeep at this site Contact Jeep and request a Build Sheet for your Jeep which should list the ratio or there should be a metal tag on each differential similar to the one in the following picture that will let you know what you've got.




For the transfer case, you either have this one : X/Sport/Sahara: NV241, 2.72:1 low range or this one: Rubicon: NVG241OR, 4:1 low range.


This one just converts tire sizes: DML Tire and Wheel Calculator

As to the benefits.

Fuel economy - This one can be tricky because the cost of a regear can be difficult to offset if your daily driving consists mainly of running around town. It can be easier to offset if you consistantly drive long distances though.

Driveability - This is for around town and on the highway. Around town, all things remaining stock other than larger tires, you will probably feel a difference in the seat of the pants aspect of aceleration from a stop and you may feel a difference when trying to pass another vehicle (passing is more of an issue with the 3.8 and automatic setup though).

Trailability - For off road. Depending on what kind of off road play you enjoy the most, you may not need to regear. If you generally run mild to moderate trails, you probably won't need to regear. If you plan to get into rock crawling and your Jeep is running 3.73 or 3.21 gears, it would probably be a good idea to regear. If you Jeep is running 4.10 gears, regearing may come down to a subjective call on your part. The main reason for regearing (generally going to lower gear ratios) is to provide more precise control when climbing over large or off camber obstacles.

I'm sure there is plenty that I missed but hopefully this will get you started.
Also, in case you don't know, when describing gear sets a numerically higher (4.10) identifier is a mechanically lower gear set and a numerically lower (3.73) identifier is a mechanically higher gear set.

For a 4.10 (or whatever the numerical identifier is) gear set, the driveshaft turns 4.10(or whatever the numerical identifier is) times for every one rotation of the tire.

With mechanically lower gear sets, the motor works harder for the same overall movement, i.e. one rotation of the tire, which produces slightly lower fuel mileage but the trade off is that more power (torque) is put to the ground.

With mechanically higher gear sets, the motor works less for the same overall movement, i.e. one rotation of the tire, which produces slightly higher fuel mileage but the trade off is that less power (torque) is put to the ground.
 

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Be careful what you read on the tuners and programmers. They do not allow you to "adjust shift points" as stated above.

As for the 4 speed always gear hunting, that is not always entirely true. It depends on tire size, terrain, and driving style. There is a difference between shifting and hunting. Shifting is okay, that's what the transmission is designed to do. Hunting is bad.

Also keep in mind when using the gear ratio calculators and various charts on the net, you must use actual tire height, not what is printed on the sidewall. Those two numbers are rarely the same and that measurement is critical for accuracy.
 

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Be careful what you read on the tuners and programmers. They do not allow you to "adjust shift points" as stated above.
By all means carefully research tuners and programmers because some, like the Bully Dog #40440, the Diablo Sport Trinity T1000 and Superchips Vivid Linq, will allow you to adjust shift points while others, like the Jet Performance stage 1 module, Superchips Flashpaq and AEV Procal simply allow you to adjust a variety of parameters such as tire size, gearing and possibly fuel maps.
 

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By all means carefully research tuners and programmers because some, like the Bully Dog #40440, the Diablo Sport Trinity T1000 and Superchips Vivid Linq, will allow you to adjust shift points while others, like the Jet Performance stage 1 module, Superchips Flashpaq and AEV Procal simply allow you to adjust a variety of parameters such as tire size, gearing and possibly fuel maps.
Sorry if I wasn't specific enough for you as most don't. That's why I said be careful.
 

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I've never used a programmer but my opinion is that your money would be better spent getting your gearing dialed in for whatever tires you plan to run. Once this is done you'll have a better idea of what, if any, power mods you'll need/want to make.

Here is a website you can use to play with some gearing numbers:

Gear Ratio Calculator (This site allows you to put two sets of numbers in so that you can do a side by side comparison.)

The information you will need for the above site:

Step 1. Transmission

Automatic trans ratios: (1) 2.84, (2) 1.57, (3) 1.00, (4) 0.69, and (R) 2.21.

or

Manual trans ratios: (1) 4.46, (2) 2.61, (3) 1.72, (4) 1.25, (5) 1.00, (6) 0.84 and (R) 4.06

Step 2. Transfer case

X/Sport/Sahara: NV241, 2.72:1 low range (listed on the site as NP241/NV241/NVG241)

or

Rubicon: NVG241OR, 4:1 low range

Step 3. You probably don't have this.

Step 4. Some common ratios are: 3.21, 3.73, 4.10, 4.88, 5.13

Step 5. Pretty much self explanatory.


And a convenient tire size converter: DML Tire and Wheel Calculator


Some basic mechanical information (depending on what you've got):

Automatic transmission is Dodge's 42RLE four speed. The main problem I've read/heard about with this transmission and larger tires against stock axle gearing is that it is constantly searching for the right gear at highway speed and is a dog when trying to pass. A programmer will help with this since it allows you to adjust shift points.

Manual transmission is the Daimler/Chrysler NSG370. I believe there were a couple of technical service bullitens (TSB) on these for correcting an issue of popping out of gear in 1st or 2nd (should be able to check your Jeeps history to see if any fixes were performed). Otherwise it is a good transmission and is still used today.

Axles:

X/Sport/Sahara front: Dana 30 with 3.21 or 3.73 gears (4.10 optional towing package in 07, 08 forward only 3.73 is optional).

X/Sport/Sahara rear: Dana 35 with 3.21 or 3.73 gears (4.10 optional towing package in 07, 08 forward only 3.73 is optional).

Rubicon: Dana 44 with 4.10 gears.

Just some axle basics: Project-JK.com - Jeep JK Wrangler Resource » Jeep JK Wrangler Axle Basics

There are also a couple of of other pages that GrimmJeeper has done that are pretty informative:

Differentials
Regearing Basics


This site has a variety of write-ups for various model year JK's: Project-JK.com - Jeep JK Wrangler Resource » Jeep JK Wrangler Axle Basics

This one has the same information as the one above but also has some user write-ups: WRITE-UP INDEX: The Quintessential Source for Do it Yourself Write-Ups


Welcome to Jeeping and thr forum!:wavey:
correction; 07 was the only year with the Dana 35 rear end, 08 and up had a non-rubi Dana 44:flowers:
 

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Discussion Starter · #18 ·
OK, I'll probably go with a 2" lift but I don't think it will solve my tire rubbing problem. The rubbing is due to tire width, not height and the rub is against the sway bar. Does that mean wheel spacers are required?
 

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OK, I'll probably go with a 2" lift but I don't think it will solve my tire rubbing problem. The rubbing is due to tire width, not height and the rub is against the sway bar. Does that mean wheel spacers are required?
Wheel spacers (Spidertrax) are required if you're running the stock wheels. You need 4.5" or less backspacing.
 

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You'll more than likely need wheel spacers, but if you're running stock, you definitely want to look at getting some lift, as it'll be hitting everything it shouldn't as soon as it flexes at all.

If you think choosing bumpers is tough, just wait until you start looking at the options for lifts!!

We've done a lot of work on TJs and JKs and can definitely help you in the short term as well as guide you on a build plan to get you where you want to be. Feel free to shoot us a PM if you'd like some extra input as you move forward.
 
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