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Discussion Starter #1
So doing my homework since I'm thinking of lifting eventually and I came across this chart on gear ratios and tire sizes.

Now what's confusing me is that my stock JKU Sport has 31" tires with the 3.23 gears which I am reading as a sub-optimal combination based on the above chart.

Is this just one of the usual stock Jeep deficiencies or am I misinterpreting the information.

Thanks!
 

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3.21 gears are only suitable for the base sport automatic with 29" tires. All the rest on oem 32's are under powered with those gears.

FCA uses 3.21 gears to simply comply with government mandated fuel consumption laws otherwise every Wrangler would have 3.73's or 4.10's as a stock gear ratio.
 

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Interesting ... so I'll be looking at lifting and re-gearing sooner than I had planned.
You will also need to replace the front carrier unless you plan to add a full locker like an ARB or EATON. The split is 3.55 - down or 3.73 - up. The rear uses a thick ring gear so it's one carrier for all ratios.

-Tim
 

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I was planning on adding lockers to the front and back eventually ...
I would recommend installing the lockers at the same time as the gears in that case. It will save you time and money so you aren't paying for labor twice.

-Tim
 

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Most people plan to do gears and lockers all at once. The labor (around $600 per axle) to put in new gears is usually much higher than the parts. If you add lockers later, you have to pay that labor all over again and may need to buy the master install kit for the lockers that you bought for the gears. It is a lot cheaper to do them at the same time and only go into the axles one time.... unless you can do the work yourself then it's a wash.

...and beat by Tim. :D
 

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Most people plan to do gears and lockers all at once. The labor (around $600 per axle) to put in new gears is usually much higher than the parts. If you add lockers later, you have to pay that labor all over again and may need to buy the master install kit for the lockers that you bought for the gears. It is a lot cheaper to do them at the same time and only go into the axles one time.... unless you can do the work yourself then it's a wash.

...and beat by Tim. :D
I just got a jk and in going over the axles,there are no axles tags on the axles.In any vehicle when I get a used one I always change the fluids so I guess I will have to do some teeth counting when I open the differentials.
 

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Discussion Starter #9
I just got a jk and in going over the axles,there are no axles tags on the axles.In any vehicle when I get a used one I always change the fluids so I guess I will have to do some teeth counting when I open the differentials.
FWIW, I checked here for the build sheet which included the stock gear ratio. If yours has been modded this may not be helpful.
 

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I just purchased a new JKUR with LT225R75/17 BFG TA tires. Are these tires considered 30" or 31" tires? Thanks for the help.
 

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Discussion Starter #11
I just purchased a new JKUR with LT225R75/17 BFG TA tires. Are these tires considered 30" or 31" tires? Thanks for the help.
I think those would be 30" (30.3 to be precise). You sure you don't have 255s? My BBE came with 245s ...
 

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I think those would be 30" (30.3 to be precise). You sure you don't have 255s? My BBE came with 245s ...
Yep, 255s. Had a senior moment when typing. I bought the Jeep almost a month ago. Drove it home from dealership and parked it in garage and it hasn't been out since.
I have a lease truck and putting miles, salt, and slush on that instead.
I want to get the Rubi undercoated and rustproofed before putting it on the road.
Again, thanks for info.
thom
 

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3.21 vs 3.73

I until recently had a 2016 Jeep Wrangler Sport and a 2015 Jeep Wrangler Sport, I just sold the 2016

The 2016 had the 3.21 ratio and the 2015 has 3.73. While people all over Jeep forums said no real difference in gas mileage, I have noticed a big difference. I had the same rims and Tires on both Jeeps, I put the stock tires and rims back on when I sold.

I am a Canuck, so we are talking metric, I have 305 65 R 17 Mickey Thompsons on both Jeeps, only 1 set capiche

I notice a very big difference in gas mileage, the 2015 I kept has the 3.73.. for the tires I have and the towing I do, I dont need more than the 3.21

just shooting breeze, but no question there is a difference in gas mileage, RPM is higher on 3.73
 

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Nutjob, how much of a difference did you notice? I got the 3.73 in my 2016 Sport. Because it's a manual I have more control on keeping the rpms low at varied speeds. Curious on how big a fuel consumption difference you noticed.
 

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Not all tire charts are made equal. Some may or may not fit your situation, check around.
WHAT you plan to do with the JEEP will have to be a major factor in deciding were you want the best performance.
 

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Nutjob, how much of a difference did you notice? I got the 3.73 in my 2016 Sport. Because it's a manual I have more control on keeping the rpms low at varied speeds. Curious on how big a fuel consumption difference you noticed.
Both my Jeeps are/were manual, I cant tell you any numbers like how many miles per gallon, I never measured, I only notice a big difference.

RPMS in the 2016 on the highway in 6th gear going 60 MPH, I had the RPM DARN CLOSE TO 1, NOW ITS DARN CLOSE TO 2

I am convinced enough that my next step is to ask how much it would cost to switch to 3.21, I bought the 2015 with the 3.73 used btw

I probably wont do it, just saying
 
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