JKUR gear ratio 4.88 or 5.13? Anyone swap to either ratio?

[Captain Chaos]

I have been contemplating which gear set to put in Number 7. I have 4.10s now, with an automatic and 35s. I do not plan on putting on bigger tires. She does pretty well now, but I don’t care for how she pulls the trailer over mountain passes. She always searches for gear. It drives me nuts. Lol
Some background; I drive a new 605hp Kenworth with 18spd all day during the week. I deliver excavators and dozers and what ever else. I’m typically 120000+ pounds. I go up and down those same mountain passes loaded and empty. I’m just having a hard time deciding.
With stock tires and gears, rpm at 70mph is 2500. With 4.88 that rpm goes to 2723. 5.13s brings it up to 2862rpm. Not a huge difference, but enough. I would like to hear from others who have done either swap. Are you happy? Would you like to have gone deeper?

 

[TreadHead Garage]

i can likely help out here, first what year is your jeep?

 

[Captain Chaos]

Sorry. It's a 2014. Knew i forgot something.

 

[TreadHead Garage]

perfect so your running a 3.6L, oh my JKUR im running 4.88 on 37's also auto. i wouldnt go any higher then 4.88 that rpms are perfect at 110KM but starts to get high and unconfortable @120km

not to mention the tooth contact gets smaller as you increase the ratio, 4.88 is stronger then 5.13 and so on. for you rig id actually recommend 4.56 if you plan on stay on 35's and maybe 4.88 if your toying around the idea of 37s

 

[Lindenwood]

Other than the above caveat of theoretical pinion strength, I always advocate for lower gears (higher numerically) than higher. I am going to be swapping some 5.29s into my 4Runner, and I'm only on 33s.

Funny enough, many folks are scared of the RPMs, but the 5.29s will actually give me roughly at the same cruising ratio as a stock 4Runner with a manual transmission and stock tires.

 

[BosCo]

I think with your background you would be happier with the 4:88 you would get a lot of engine hum with the 5:13. I am currently running 4:56 with a 6 spd and stock tires (35's have been pulled off due to I am picked about tires and handling) and at 75mph it is about 2800 rpm. So my Point being it would be pretty close to the same in my opinion.

 

[EarlSwagger]

I’m running 4.56 in my 2016 JKUR. I am glad I didn’t go higher. She seems to run thru gears quick as it is. And at cruise speed the 2700 rpm is about perfect for 65-mph. My vote would be the 4.88 out of your choices.

 

[Captain Chaos]

I’m definitely leaning towards 4.88s. I want more power pulling, so 4.56 is out. I’m going to build a teardrop this winter, I’m sure it will be heavier than my Bantam. I can’t see how it would be lighter.
4wheel parts has a gear change special for $1299. That’s for front and rear. Hard to beat $1300 to do a gear swap. I’ve never heard of the brand though. Genuine Package? Something like that.

 

[TreadHead Garage]

I’m definitely leaning towards 4.88s. I want more power pulling, so 4.56 is out. I’m going to build a teardrop this winter, I’m sure it will be heavier than my Bantam. I can’t see how it would be lighter.
4wheel parts has a gear change special for $1299. That’s for front and rear. Hard to beat $1300 to do a gear swap. I’ve never heard of the brand though. Genuine Package? Something like that.

Just my opinion being in the industry, buy the best parts you can. A blown diff leaves you dead in the water, not something to cut cost on.

On avg we quote 2300$ CAD for a regear with solid pinion spacers no crush sleeves

 

[Captain Chaos]

Just my opinion being in the industry, buy the best parts you can. A blown diff leaves you dead in the water, not something to cut cost on.

On avg we quote 2300$ CAD for a regear with solid pinion spacers no crush sleeves

Oh, I hear ya. 4wheel parts stands behind them though. I’m thinking Yukon, or G2. Same gear, different box.

 

[TreadHead Garage]

Oh, I hear ya. 4wheel parts stands behind them though. I’m thinking Yukon, or G2. Same gear, different box.

I personally run and sell nitro gear, yukon has notoriously been solid. G2 kinda worries me.

 

[Captain Chaos]

G2 is supposed to be made in the Yukon factory. Different box.

 

[v_man]

Go low. I have 5.29's albeit in my 4 cylinder Toyota crawler. The whole argument that 4.88's are somehow marginally stronger than say 5.13 is silly in my opinion. It's been debunked numerous times if you look into it. It's also a silly argument if you have other weak links in your stock axles like your U-joints or shafts.

Ease off the gas pedal a few miles per hour on the highway and your RPM's are right back where they'd be with higher gears. I've learned to just slow down on the highway, it saves gas in all regards.

I've yet to come across anyone in the 4x4 community who regrets going as low as they did, but plenty of folks who wish they'd gone lower. Gears are one thing you want to do right. and do once. My 2 cents...

 

[Captain Chaos]

Go low. I have 5.29's albeit in my 4 cylinder Toyota crawler. The whole argument that 4.88's are somehow marginally stronger than say 5.13 is silly in my opinion. It's been debunked numerous times if you look into it. It's also a silly argument if you have other weak links in your stock axles like your U-joints or shafts.

Ease off the gas pedal a few miles per hour on the highway and your RPM's are right back where they'd be with higher gears. I've learned to just slow down on the highway, it saves gas in all regards.

I've yet to come across anyone in the 4x4 community who regrets going as low as they did, but plenty of folks who wish they'd gone lower. Gears are one thing you want to do right. and do once. My 2 cents...

Very true. 5.38 is where you start breaking pinion shafts on a Dana 44. Way lower than I want to go. I don’t mind sacrificing a few rpm to have the ability to comfortably pull passes. My mileage sucks anyway.

 

[Inthewoods]

Been rock crawling for years and I'll go with the 4.88's and 35s. I had 4.88 in my Fj40 with a 4.0 rebuilt and kit and a locker in the rear and it did fine. 50 mph up steep grades but in 4x did great. Did CA hardest trails with that set up.. I had a 53 willy's pick up with a Mustang 302 and 5.38s and 31's the rpm were to high and blow the motor before I put bigger tires on. In 4x with 5.38s I hit the back and front windows with my head when I touched that gas pedal. 5.38 with a 4 banger yeah. Add a better air intake and headers and exhaust and these can be the extra HP you need to be happy. Heck I even changed the whole distributor gear unit with a racing one. At any elevation I can be at peak power in 2 clicks. My 1.275 cents

 

[Lindenwood]

Been rock crawling for years and I'll go with the 4.88's and 35s. I had 4.88 in my Fj40 with a 4.0 rebuilt and kit and a locker in the rear and it did fine. 50 mph up steep grades but in 4x did great. Did CA hardest trails with that set up.. I had a 53 willy's pick up with a Mustang 302 and 5.38s and 31's the rpm were to high and blow the motor before I put bigger tires on. In 4x with 5.38s I hit the back and front windows with my head when I touched that gas pedal. 5.38 with a 4 banger yeah. Add a better air intake and headers and exhaust and these can be the extra HP you need to be happy. Heck I even changed the whole distributor gear unit with a racing one. At any elevation I can be at peak power in 2 clicks. My 1.275 cents

Sorry to say, but a 10% increase in highway RPMs for a few months is not what blew your engine ;) .

As to the FJ40, you also had probably the torquiest FJ around with a soupedd-ep 4.0 in there ;) .

 

[Inthewoods]

Lindenwood, it was over 30 years ago but I think I throw a rod in that 53. A little more detail might help. It still had the banjo rear end and the stock T 90 trans and the 205 with twin sticks, nothing like today's transmissions. No overdrive, didn't install one yet. No highway, If I remember correctly my top speed was in the 50's no faster and I did PUSH it so that didn't help. My 46 Willy's with a flat top 4 had a top speed of about 46 mph pushing it with larger tires. Now the FJ40, I did spend more on it then these Rubicon today. I wasn't into horse power just torque. The motor was machine out to spec for torque with crank and cam kit and painted and chromed to match the FJ. I replace the clutch and distributor with a racing ones. The FJ had a lot of extras and these were my beginning projects of the 8 that I did, my dodge #9. I think your right with these newer transmission there won't be a big change in the rpm. I'm not into these new jeep or know much about them. They are nice.
Do we ever completely finish building a rig?

 

[Lindenwood]

Do we ever completely finish building a rig?

I can think of $10,000 in desired 4Runner gear off the top of my head, so nope :P .

Nice build!

 

[rgk401]

4.88 Yukon gears in a 2012 Jeep Jk with a manual transmission and I’m getting 18-21 mpg with 35x12.5x18

 

[ovrlndr]

My buddy in a 2015 auto on 37s put in 5.13s and he's been happy with it. I'm in a 2015 6mt on 35s and I will be going to 4.88s whenever I regear and will be going to 37s when I get new tires...