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Discussion Starter · #1 ·
Thinking of re-gearing my 17 Sahara. I currently have 3.73's, thinking of going to 4.10's so I can put 35's on it. It's a DD, and I won't be doing any rock climbing. According to the gear chart I saw, 4.10's will handle the 35's and still keep my rpm's down around 2280 at 70 mph.

Question - is it the same 4.10 gear set for both the Dana 30 and Dana 44 axles? Or is there a different 4.10 set for each?

What can I expect to pay a shop to do this? I'm in Florida.
 

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Don't go less than 4.56. I have 4.88s in my JKUR with 35s with no plans of going to 37s. I absolutely love my 4.88s. I had 4.10s before. No way I'd pay to have 4.10s put in I feel I were you. Also, the gears are definitely different. Even on a Rubicon, the gears are different on the front vs rear.
 

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Discussion Starter · #3 ·
Don't go less than 4.56. I have 4.88s in my JKUR with 35s with no plans of going to 37s. I absolutely love my 4.88s. I had 4.10s before. No way I'd pay to have 4.10s put in I feel I were you. Also, the gears are definitely different. Even on a Rubicon, the gears are different on the front vs rear.
So you're saying there are different part numbers for 4.10's for Dana 30, and 4.10's for Dana 44's? That's good to know!

Don't the 4.88's cause your rpm's to be up in the 2800 rpm range? Doesn't that kill your mileage?
 

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I re-geared to 4.10's from 3.21 on my JKU Sport daily driver last month, I just go down dirt roads to camp sites, no rock crawling. More than happy with the 4.10's on 33's.
I bought these gears from Revolution. So far no problem, Just a ringing noise at 40 mph that stops above and below that speed. Other Jeepers tell me it will stop once they are broken in.
Revolution Gear Package 4.10's With KOYO Kits for Jeep JK Non-Rubicon(D44/D30) | eBay
 

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For 35s, I vote for 4.56 (4.88 if you're in a real mountainous area) . For some reason, I even think the 4.10 kits are more money than 4.56.

Both axles need to have need have the same gear ratio. Part numbers will be different though. I recommend Letting the shop that's doing the install order the parts. That way if the wrong part is ordered, then it's on them to make it right.

If you're considering TrueTracs or Lockers sometime in the future, you should have them done the same time that you re-gear.
 

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Don't go less than 4.56. I have 4.88s in my JKUR with 35s with no plans of going to 37s. I absolutely love my 4.88s. I had 4.10s before. No way I'd pay to have 4.10s put in I feel I were you. Also, the gears are definitely different. Even on a Rubicon, the gears are different on the front vs rear.
So you're saying there are different part numbers for 4.10's for Dana 30, and 4.10's for Dana 44's? That's good to know!

Don't the 4.88's cause your rpm's to be up in the 2800 rpm range? Doesn't that kill your mileage?
The front and rear part numbers are different even if you have two D44s. My RPMs are about 2750 at 70 mph. About 3100 RPMs at 80 mph. However, my engine isn't lugging along and the transmission isn't constantly shifting either. So far, I'm getting about 14 to 15 mpg with the 4.88s. I was getting 13 to 14 with the 4.10s due to all of the lugging and shifting I guess. With the 4.10s, you're climbing a hill on the interstate and it's having to down shift and running 4500 RPMs! That kills your mileage.
 

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Going to 35's will probably reduce your mpg. Once you do that, going to 4.56 or 4.88 will not additionally reduce your mpg. In some cases it may actually improve vs 35's and 3.21's. But the main benefit to adjusting your gearing to compensate for bigger tires is that it counters the performance loss that comes from having the wrong gearing (which you have if you have 3.21's and go to bigger tires) Anything over 29" or 30" tires will work better with something other than 3.21.
If you look at a typical chart for the gearing, at 70 mph each step in gearing is worth around 200 rpm. But 4.56 or 4.88 is what most people want for 35's. Some will want 5.13, but that is more for manuals and slow crawling. It is still only 200 rpm more at 70 mph than 4.88, but it probably won't be for most.
 

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Like others have said, don't waste your money on 4.10's. 4.56 is most likely where you will want to be IMO.

I run 4.56's on 35's and it drives really well at hwy speeds. I rarely drive over 65 but at 70 I am still under 2700. I get upwards of 17 mpg (at 65mph) highway. Typically for mixed city/hwy, right around 15 on average.

If you aren't doing the regear yourself, have the shop order the parts. However most decent vendors have regear kits. You just need to tell them what vehicle model you have and they already have a setup. I ordered my complete gear setup with the rebuild kit from Northridge 4 x 4.
 

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Discussion Starter · #9 ·
Thanks for all the replies! I've learned a lot. I'll probably go with the 4.56's. Living in Florida, my Jeep has never seen a hill. 99% of my driving is 70-75 on the flat interstate!
 

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Thanks for all the replies! I've learned a lot. I'll probably go with the 4.56's. Living in Florida, my Jeep has never seen a hill. 99% of my driving is 70-75 on the flat interstate!
4.56 is a good choice with the 35's. That is what I would have gone with if I had went to 35's and not the 33's
 

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If you never leave Florida then you can live with 4.10 and 35's, even 3.73 might be ok. I would get you wheel/tire combination and give it a shot. But like others I would recommend at least 4.56 gears.

For 35's

4.56 - live in flat country, don't visit the mountains often.

4.88 - live in hill country, in the mountains often

5.13 - live above 5000 feet and don't visit the flat country
 

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Thanks for all the replies! I've learned a lot. I'll probably go with the 4.56's. Living in Florida, my Jeep has never seen a hill. 99% of my driving is 70-75 on the flat interstate!
My 4.10s were okay here in Oklahoma. It's not quite as flat as Florida but still pretty flat. I went with 4.88s because my Jeep is heavy. Bumpers, winch, full set of skids, etc. I also travel to Colorado and Utah often and the 4.10s were not a lot of fun there. I also plan to tow a trailer someday. If I lived in Florida, I'd do 4.56. I think 4.56 is the absolute sweet spot for a JKU. I still really like my 4.88s though and it was a huge improvement over 4.10s. 4.56 will be a huge improvement over 3.73 too
 
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I ran 35s and 3.73s for about a year and a half. To me, it wasn't worth paying to have front/rears done until I was ready to add lockers and also move to 37s. Now I run 4.88 (heavy JKU, auto and 3.6L). I don't regret 3.73 and 35s...it wasn't bad at all. Esp after adding the flashcal to the mix. I traveled across the country and did some pretty epic Colorado mountain wheeling....and got along fine.

I'll agree it's not a "textbook" setup...but I wouldn't hesitate to do it again.
 

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I ran 35s and 3.73s for about a year and a half. To me, it wasn't worth paying to have front/rears done until I was ready to add lockers and also move to 37s. Now I run 4.88 (heavy JKU, auto and 3.6L). I don't regret 3.73 and 35s...it wasn't bad at all. Esp after adding the flashcal to the mix. I traveled across the country and did some pretty epic Colorado mountain wheeling....and got along fine.

I'll agree it's not a "textbook" setup...but I wouldn't hesitate to do it again.
I am currently running a 3.73 with 35" tires. The 3.73 came with the tow package from the factory and I thought I'd give it a try with my lift kit and tire upgrade. So far so good. I do mostly highway and city driving with some mild off-roading in Michigan. I've also done 300+ mile road trips to the top of the UP. I'm not opposed to changing my gear ratios, but i'm not seeing a strong reason to do so.....yet. When that time comes, I'll probably go 4.56.
 

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I DD my 2013 JKU with 4.56's, and in my opinion, they're perfect for my driving style and 35's, i have a long commute everyday, and i offroad most weekends, mountain and rocks included, but not Colorado elevations though, i don't do any towing, however i do have a Jeep that is 400lbs heavier than the the factory with an auto trans, and so far i haven't have any regrets with my choice for the past 40k miles or so since i've had them, MPG wasn't bad at all until recently, and i watch my MPG like a hawk, i can say, the more detrimental item that will affect your MPG as a whole, would be your tires, then your aerodynamics (lift, racks and things that affect you drag coefficient), then gearing, combine everything, and your mpg will always drive down, not up :), i was running KO2 in 315/70/17 before, and switched to Nitto TG's, i've lost 2mpg consistently, i was at high 19's to low 20's stock, low to mid 18's with K02's in 285/70/17, high 16's low 17's with KO2's in 315/70/17, 2"-2.5" lift and 4.56's, and now hi 14's to mid 15's with the only difference being the Nitto TG's in 315/70/17

This what to expect if you had an auto JK with 4.56 and 35's at 70mph, 2650-2700rpm

http://www.youtube.com/watch?v=6paKiCJvq40
 

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Thanks for all the replies! I've learned a lot. I'll probably go with the 4.56's. Living in Florida, my Jeep has never seen a hill. 99% of my driving is 70-75 on the flat interstate!
What about those intracoastal bridges? ;)
 
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I have 35s with 3.21s as a daily driver and have no problem at all. And as far as gas mileage i still hang out around 18 to 20 mpg depending on highway or city driving. Other than adding the extra weight i havent noticed much difference in power. Maybe a very slight decrease like i said due to extra weight.
 

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I have 35s with 3.21s as a daily driver and have no problem at all. And as far as gas mileage i still hang out around 18 to 20 mpg depending on highway or city driving. Other than adding the extra weight i havent noticed much difference in power. Maybe a very slight decrease like i said due to extra weight.
You are significantly undergeared for that size tire. Because you are undergeared, you are putting a lot more wear and tear on the engine and transmission. You spent a lot of money on a new Jeep, and a lot of money on big tires - why not treat it right and gear it properly?

The difference between 3.21 gearing with 35s and the 4.56 the original poster appears to have decided on is astronomically HUGE. I personally would do 4.88 with 35s even, especially if an automatic.

The difference at 70mph: 3.21 - 1791 rpm, 4.56 - 2544 rpm, 4.88 - 2723 rpm. It's almost a 50% difference just going to 4.56.
 

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Thanks for all the replies! I've learned a lot. I'll probably go with the 4.56's. Living in Florida, my Jeep has never seen a hill. 99% of my driving is 70-75 on the flat interstate!


The 4.56 will serve you well on the east coast. I'm near Cleveland in the hills, and my 16 JKU 4.56 auto (from 3.21) goes up and down hills effortlessly and rarely ever needs to downshift. I'm a lazy cruiser, but I have hit it a few times. No slouch. On highways 70-75 about 2700 rpms and avg 16.7 mixed driving.

Was out and about in Denver Colorado area, and driving around I would want more, and would go with 4.88. Huge difference in performance when you drive in the elevations.

Here in Ohio and in the mountains in New York and PA, I never need more than the 4.56. For me anyhow

I couldn't imagine 3.21 out west.. 🤢


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