Re-gearing for 35inch tires

Sjcristi88

Sjcristi88

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May 10, 2021
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New York
Hey JK fam,
I’m looking to upgrade my 2016 Sahara that has just over 76k miles on it. I’m looking to change my stock 32s with some 35s on a 2.5 inch lift. I use my rig to DD and really won’t be using it to go off roading. More of an aesthetic project.
However, since I am new to this I didn’t realize I may have to do some re- gearing to make this work. My first two questions are is this necessary and if so how much would this cost to install?
What are some other things I should consider when installing 35 inch tires on a 16 Sahara? Should I just go with the 33s to avoid the extra hassles?
Thanks for the help guys. Much appreciated.
 
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What is your current gear ratio? If you have 3.73's, it may be tolerable depending on the terrain. I have a 2016 2dr Sport with a 2.5" lift, 35's and 3.73 gears and an automatic. I have some hills around me and it's not too awful. I do plan on regearing, just haven't yet and it's been 2 years.

As far as cost, find a good 4x4 shop near you & get a quote. Then get a couple more :). I was quoted don't recall what I was quoted around $1300 for parts and labor.

Nice thing about a 2.5" lift is that it is mild enough that it shouldn't require a lot of other changes. I have an AEV lift with geometry correction brackets and it drives great. Invest in a quality lift from a reputable company, others can chime in on their experience.

Lastly, with 35's, might be a good idea to upgrade to HD ball joints. The added weight of the bigger tire will stress an already marginal part.
 
You will have to recalibrate your speedometer if you go bigger tires. Like Jerry said it depends on what gears you have in your JK now.
 
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I just went thru this. 2015 JK 2 door soft top. Installed 35" tires in place of the 32's. Mine is a DD also with no plans to off road it. It seemed to drive fine after I installed the tires, only rubbed slightly on the front bumper which I replaced.I was told it could stay as is since Iwasn't going off raod but I wanted to lift it. I went with a 2.5 lift installed by a local 4 X 4 shop. I reprogrammed for the speedometer. I have 3.21 gears, do notice a difference in power, it is liveable but will be upgrading to 4.56 gears within the next 60 days. Gas mileage dropped from 19.6 to 17.8. Not sure how much worse it will be with the 4.56 upgrade.
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BLACKJKU said:
You will have to recalibrate your speedometer if you go bigger tires. Like Jerry said it depends on what gears you have in your JK now.
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Yeah, I believe I have the 3.2.1 gear ratio. I heard all I would need is to get installed is a “Super Chip Tuner”. Once installed it would recalibrate the speedometer to the 35s. I don’t know if that’s all I would need.
 
Sjcristi88 said:
Yeah, I believe I have the 3.2.1 gear ratio. I heard all I would need is to get installed is a “Super Chip Tuner”. Once installed it would recalibrate the speedometer to the 35s. I don’t know if that’s all I would need.
Click to expand...

You can also get a JScan then I hear you can make other changes in your ECM also.
 
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Sjcristi88 said:
Hey JK fam,
I’m looking to upgrade my 2016 Sahara that has just over 76k miles on it. I’m looking to change my stock 32s with some 35s on a 2.5 inch lift. I use my rig to DD and really won’t be using it to go off roading. More of an aesthetic project.
However, since I am new to this I didn’t realize I may have to do some re- gearing to make this work. My first two questions are is this necessary and if so how much would this cost to install?
What are some other things I should consider when installing 35 inch tires on a 16 Sahara? Should I just go with the 33s to avoid the extra hassles?
Thanks for the help guys. Much appreciated.
Click to expand...
If you have 3.73, which I suspect as it's a Sahara, you don't need to regear if you're not off-roading. I have a 14 Sahara, auto with 3.73 and 35's and I do some overlanding and lighter trails (no rock-crawling) and it runs great, and I can run 70 on the interstate at less than 2500rpm.
You could go to a 4.11, but for a DD I don't think it's worth it. Spend the money on a Peddle Commander and see what a difference that makes.
 
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If I remember correctly JScan allows for 1/4" increments when entering new tire diameters, which effects shift points and the speedo.
Do yourself a favor and don't assume your tires are 35" in diameter. Once they're installed and you have a full tank of gas, put 2 people in your Jeep and measure all 4 tires from the ground up and average the height to the nearest 1/4" and use that to reset the ECU. It'll keep your shift points as economical as possible and speedo as accurate as possible.

Also, if you air up after some off-roading, you should re-measure. And re-measure every year- age on the tires as the tread wears.
 
When I recaliberated mine I just used what my GPS was saying that I was doing and then set the speedometer to that. Took a couple trys to do it but it's right on with the GPS.
 
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Anybodyhome said:
If I remember correctly JScan allows for 1/4" increments when entering new tire diameters, which effects shift points and the speedo.
Do yourself a favor and don't assume your tires are 35" in diameter. Once they're installed and you have a full tank of gas, put 2 people in your Jeep and measure all 4 tires from the ground up and average the height to the nearest 1/4" and use that to reset the ECU. It'll keep your shift points as economical as possible and speedo as accurate as possible.

Also, if you air up after some off-roading, you should re-measure. And re-measure every year- age on the tires as the tread wears.
Click to expand...
Thank you for the response Anybodyhome. Just to see if I’m understanding this properly, if I follow your advice. I don’t have to get my Jeep re geared ? Is there a difference between the regearing and installing the Jscan ?
For DD the Jscan would be more ideal for my driving routine. What is an ECU ? Thanks for the help
 
Regearing is changing the front & rear gears in the differentials, Jscan is still needed after that to tell the onboard computer what RPM the transmission needs to shift at. With oversize tires it is the same thing basically. So do your jeep a favor and get the Jscan app
 
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Sjcristi88 said:
I don’t have to get my Jeep re geared ?
Click to expand...
You never have to get your Jeep re-geared. If you have a Sahara, I believe your gears are 3.73, which is fine with 35s as a DD. Nonetheless, enter your VIN here and get a build sheet for your JK, it'll tell you your gear ratio, among other things:
https://www.vindecoderz.com/EN/Jeep/WRANGLER

Sjcristi88 said:
Is there a difference between the regearing and installing the Jscan ?
Click to expand...
JScan is an app that's used in conjunction with an onboard plug-in adapter that is used to diagnose and change factory settings to the electronic brains that operate your JK. Your speedometer is based upon the RPMs of your tires, your transmission is also shifting based upon the speedometer and tach. If you get larger tires, your speedometer will be inaccurate and your transmission will shift when it shouldn't.
Learn more about JScan here:
http://jscan.net/

The OBD II scanner I have:
https://www.amazon.com/gp/product/B06XGB4873/?tag=jkforum-20

This and your phone will become lifelong friends in your JK. Just about every aspect of driving and using your JK can be controlled with these 2 things. When you put those 35s on, you'll be able to measure and input your new tire size so your speedometer is accurate and the transmission will shift at the correct time. You can set your daytime running light configuration (believe it or not, insurance companies give you a break for DRLs in some states). You can turn off the seat belt alarm, you can reset your TPMs when you run those new 35s several pounds lower than the tire guy says because it rides better....
 
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Ditto to all of the above on the JScan app. Download the app for free but then you have to pay around $25 to register your VIN, then the bluetooth OBDII will cost around $35 depending on which one you choose.
We have 35s and I entered like 34 or something to get the speedo right. I had to change it a few times to fine tune it.
As for the other things, yes I disabled the TPMS and programmed a new key!
The trail mode is nice too as you can monitor Temps and such on a single screen.
You definitely need to get it!
 
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