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Discussion Starter #1
Beat to death, but couldn't find my exact situation.

JKUS 2013 automatic, 315/75r16, and I'm looking to go from 3.21 to 4.56 or 4.88.

  • Steel bumpers/side steps/70lb rack
  • Max 500ft above sea level most months out of the year. 70/30 city/highway driving
  • it's my DD, no rock crawling, only over-landing/beach
  • Will 4.88 be too much for the 315/75r16s(34.6") for now? Super hesitant on going 4.88 over 4.56
  • Yukon Gear kit/Install kit + open carrier
Thanks!
 

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You will to decide for yourself. However, I have a 2015 jk with 35", and I went with 4.56. it is a daily driver and work is about 45 minutes mostly highway. I was concerned about losing top end speed.

I am happy with my choice. At 70 mph, I am at about 2700 or 2800 rpms. I think if I went 4.88 it would be higher than that and would be too much for my needs. I am pretty happy that I have 6th speed back. Ever this weekend in the Georgia Mountains, I am only dropping to 4th of 5th or steep inclines. Btw I have a manual.

Good luck.

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4.56 would be my choice... No mountains, no altitude.
 

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I have a 2013 JKU with auto trans and 35’s, so your exact setup. I ran with stock 3.21’s for nearly 5 years before re-gearing. My initial plan was 4.56, but decided last minute to go with 4.88’s. If I were to do over, with no thoughts of going to 37’s, I would do 4.56’s.

My job supplies a car, so I only drive the Jeep for pleasure, but during the summer it rarely sits more than a day at a time. It spends most of its time on the pavement, sees the trails occasionally, and is on the beach for a week pretty much every summer.

Around town, the 4.88’s are great. The difference in power and acceleration is soooo much better than stock. Once I start driving over about 50 miles an hour though, I feel like I need a 6th gear. On the highway at 70-80 MPH, I am pretty sure that I am turning higher RPM’s in 5th gear than I did running in 4th gear with the 3.21’s. My fuel mileage has dropped significantly since the re-gear.

Don’t get me wrong, I don’t think my Jeep should be a race car, a highway cruiser, or a gas sipper, but I think that 4.56 gears would have given me a sufficient increase in performance without running the engine quite so hard at highway speeds.

Some will tell you go 4.88’s. For me, I would rather the trans have to drop into 4th on a highway hill climb and run lower RPM’s on the flats than to be able to hold 5th on the hills, but always be turning close to 3k RPM’s.

Whichever you decide, you will definitely feel the difference over your stock gears.


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I am thinking 4:56 would be your best bet.
I would also consider traction adders while you are at it.
 

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I debated going from 3.21 to 4.11 or 4.56? I already knew I was going to run 285/75/17 so it was a tough call for me. After lots of recommendations from people here and the shop doing the work I finally went with 4.56. Yea I lost a couple mpg's but overall it's worth it imo. I do a fair amount of towing and with the 4.56's it sure is a lot easier on my jeep. My jeep is so much more enjoyable to drive with the 4.56 but I do live where there's lots of hills.
 

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Discussion Starter #7
I have a 2013 JKU with auto trans and 35’s, so your exact setup. I ran with stock 3.21’s for nearly 5 years before re-gearing. My initial plan was 4.56, but decided last minute to go with 4.88’s. If I were to do over, with no thoughts of going to 37’s, I would do 4.56’s.

My job supplies a car, so I only drive the Jeep for pleasure, but during the summer it rarely sits more than a day at a time. It spends most of its time on the pavement, sees the trails occasionally, and is on the beach for a week pretty much every summer.

Around town, the 4.88’s are great. The difference in power and acceleration is soooo much better than stock. Once I start driving over about 50 miles an hour though, I feel like I need a 6th gear. On the highway at 70-80 MPH, I am pretty sure that I am turning higher RPM’s in 5th gear than I did running in 4th gear with the 3.21’s. My fuel mileage has dropped significantly since the re-gear.

Don’t get me wrong, I don’t think my Jeep should be a race car, a highway cruiser, or a gas sipper, but I think that 4.56 gears would have given me a sufficient increase in performance without running the engine quite so hard at highway speeds.

Some will tell you go 4.88’s. For me, I would rather the trans have to drop into 4th on a highway hill climb and run lower RPM’s on the flats than to be able to hold 5th on the hills, but always be turning close to 3k RPM’s.

Whichever you decide, you will definitely feel the difference over your stock gears.


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Great thanks for the info.

No thoughts of true 37s since 16" wheels is a lil awkward for selection for A/T tires, loving the Duratracs right now and checking out the Ironman's next (buddy has them and love em)

How would you compared 4.56 to 4.88 for back country city driving? It's all 30-45mph in my immediate area
 

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Discussion Starter #8
I am thinking 4:56 would be your best bet.
I would also consider traction adders while you are at it.
+1 on 4.56 I think i'll be going in that direction.

what are traction adders? I'm intrigued, do tell. Have just heard about adding lockers but not going in that direction due to my application
 

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I meant truetracs front and rear.
Some people like powertrax (I think that is what they are) as an alternative to truetrac.
If you add one to the front, you don’t need to spend the $80 to $100 for a new carrier.
 

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Discussion Starter #10 (Edited)
I meant truetracs front and rear.
Some people like powertrax (I think that is what they are) as an alternative to truetrac.
If you add one to the front, you don’t need to spend the $80 to $100 for a new carrier.
oh ok, I'm still getting the lingo down ;)

having said that, do you think I need them for my application?

The reason I wasn't even considering truetracs is 2-fold. I have zero interest in rock-crawling, and really just stick to pavement, sand and seldom trails. The other reason was because I keep coming across forums where those who have put in lockers in their automatic '13-'18 have had nightmares with their transmission going into limp mode, computer communication, and not being able to sort out the issue with a tuner and experienced mechanics. That right there has me like "nope, not dealing with that"
 

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We use our JK similar to you.
We use it as a DD, but do have a few other vehicles so it's not used every day.
We do overland style off-roading.
Several years ago, Mopar was offering crate axles, so I went with them.
Dana 44's, with 4.10 and e-lockers.
I did wire the lockers stand alone, rather than into the Jeeps nanny system.
For where we are, and how we use our JK, the 4.10's work good for us.
 

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oh ok, I'm still getting the lingo down ;)

having said that, do you think I need them for my application?

The reason I wasn't even considering truetracs is 2-fold. I have zero interest in rock-crawling, and really just stick to pavement, sand and seldom trails. The other reason was because I keep coming across forums where those who have put in lockers in their automatic '13-'18 have had nightmares with their transmission going into limp mode, computer communication, and not being able to sort out the issue with a tuner and experienced mechanics. That right there has me like "nope, not dealing with that"
In my experience, sand is a super place for a gear LSD. I like the Powertrax Grip Pro... It's a little less expensive than the TrueTrac without giving up anything. And if you already have to drop $100 for a new front carrier, it makes the upgrade much more reasonable. Invisible unless you are in 4WD then only engages when you need it....

 

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Great thanks for the info.

No thoughts of true 37s since 16" wheels is a lil awkward for selection for A/T tires, loving the Duratracs right now and checking out the Ironman's next (buddy has them and love em)

How would you compared 4.56 to 4.88 for back country city driving? It's all 30-45mph in my immediate area
My choice would still be 4.56.


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oh ok, I'm still getting the lingo down ;)

having said that, do you think I need them for my application?

The reason I wasn't even considering truetracs is 2-fold. I have zero interest in rock-crawling, and really just stick to pavement, sand and seldom trails. The other reason was because I keep coming across forums where those who have put in lockers in their automatic '13-'18 have had nightmares with their transmission going into limp mode, computer communication, and not being able to sort out the issue with a tuner and experienced mechanics. That right there has me like "nope, not dealing with that"
I didn’t have any issues adding a selectable locker. This is the first time I’ve heard that it could cause problems. Maybe you are thinking about more of a lunchbox locker.


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I didn’t have any issues adding a selectable locker. This is the first time I’ve heard that it could cause problems. Maybe you are thinking about more of a lunchbox locker.


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Lunchbox (auto) locker in the front, non issue, works great... In the rear? All kinds of problems with the nanny systems.
 
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