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Impressions from a 5.13 gears install on a JL Wrangler Unlimited Rubicon (JLUR)

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wibornz

wibornz

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4.10 was fine with my 37, then I started pulling a camper and added heavy steel bumpers, winch and gear for traveling. Unloaded around town is fine with 4.10 gears on 37s.
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What I find kinda funny.....at first, people were saying (with an automatic) "run 37" tires with stock 4.10 and you are fine". Then came the "4.88 is plenty" and now... "5.13 are the way to go".

I'm going with 4.88 with 37's since that's 5% lower than stock ratio with 33's. There's only another 5% lower advantage with 5.13's.
There’s nothing wrong with driving around with 37s and 4.10s. Your transmission is going to hunt for gears more, you will see 8th less in several conditions but your transmission is not going to break on you.

4.88 would be a good upgrade for most people. 5.13s will be the way to go for people with plans to make their rigs heavy and or live in terrains that would make them benefit from it.

After all, what really matters is that you are happy with the way your Jeep runs.

Could I have gone with 4.88s? Yes, but I have long term goals for this Jeep and would not want to re-gear again in the future. It was important to me not to regret the gear ratio in the future. I am happy with my decision and would not change a thing. The Jeep drives great in town and is not anywhere close to being over-revved in the highway.

Everyone is going to have a different opinion. Contact a local Jeep club, go to a meetup and get on jeeps with different gear ratios and similar setups to what you plan to have. It is really important that you go through that and make an educated decision based on your own experience. There’s nothing worst than regretting an expensive upgrade.
 

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This too is on my wish list. I'm running 37s with 2.5 in lift on the 8 speed auto with stock 4.10s. Everything around town and on the highway was fine until I got on the Ohio Turnpike. Cruise at 72 and you see 8th quite often, then down to 7th on the slight inclines. Now cruise at 78 to 80 on the turnpike, I rarely touch 8th gear and if there is a headwind i go all the way down to 6th. I get about 14 mpg on the turnpike.

I tried to fool the computer by manually shifting up to 8th. It went up and stayed there; but the instant MPG gauge dropped from 14.something to 13.something....

The great thing about the 8 speed is the range of ratios. With an old 6 speed or 5 speed you'd really have to pinpoint your gear and you'd be sacrificing either low end torque or high speed MPG. This question of which gear to choose is A LOT more important to a Manual 6 Jeeper...

That being said, a lot of good feedback here on this post. Thanks big fella...
I have had the same experience with my 2018 JLU Rubicon with 2” Mopar lift, 37” tires, and stock 4.10 gears. 8th gear is only used around town and is rarely seen on the highway. Can only get into 8th on flat ground or downhill with no wind. On windy days it stays in 6th gear for a while before shifting to 7th. It sucks on the highway if I’m going over 65 mph.
 

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There’s nothing wrong with driving around with 37s and 4.10s. Your transmission is going to hunt for gears more, you will see 8th less in several conditions but your transmission is not going to break on you.

4.88 would be a good upgrade for most people. 5.13s will be the way to go for people with plans to make their rigs heavy and or live in terrains that would make them benefit from it.

After all, what really matters is that you are happy with the way your Jeep runs.

Could I have gone with 4.88s? Yes, but I have long term goals for this Jeep and would not want to re-gear again in the future. It was important to me not to regret the gear ratio in the future. I am happy with my decision and would not change a thing. The Jeep drives great in town and is not anywhere close to being over-revved in the highway.

Everyone is going to have a different opinion. Contact a local Jeep club, go to a meetup and get on jeeps with different gear ratios and similar setups to what you plan to have. It is really important that you go through that and make an educated decision based on your own experience. There’s nothing worst than regretting an expensive upgrade.
Solid post...I did a little test yesterday in my 6 speed with 4.10s on 37s/beadlocks at 26psi to simulate 5.13s cruising 70mph at 2500rpm and 4.88 at 70mph/2350rpm. In 4th gear, I was at 65mph at 2500 rpm and definitely had power accelerating. At 58mph, it was at 2350 rpm and it still accelerated well, but obviously not as good as 2500rpm. It seems like the 3.6 motor starts making useable power at 2000 rpm's. My jeep isnt a daily driver and has about 400lbs of added weight with beadlocks, steel bumpers/sliders, winch. I live on a mountain with 1200' elevation gain from bottom to top and regularly drive up and down it at 35mph + some hwy driving at 75mph. I like the 37" tire on this jeep/axles and dont plan to go bigger. If 4.88 and 5.13 both provide useable power in 6th gear, my main concern is will the 4.88s idle over obstacles in 1st gear?

I have a friend with a JL who has done the rubicon and 15+ badge of honor trails all over the country with 4.88s/6 speed on 37s/beadlocks and he said it idles over obstacles well and will chirp the tires before it stalls. He feels 5.13 is overkill on 37s and you're simply losing some 70+mph efficiency and aren't really gaining anything meaningful offroad. If that's the case, 4.88 seems to be the ticket combining crawling and hwy efficiency.

How heavy is your rig with 5.13s?
 
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Suchestom

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I have a 2019 JLUR that has 4 1/2 inch terraflex lift, Rockhard Patriot full width bumpers (1/4 inch thick) front and rear, 10000 pound warren winch, Jerry cans and carrier on the back, Rockslide steps with extra protection armor, 37 BFG's on true Beadlocks, among other accessories, so I'm pretty heavy. I regeared with DANA / SPICER gears to 5:13s and couldn't be happier. I also added a RIPP Supercharger. The combination works excellent. I never felt like 4 low crawling ratios were a problem, but I was not happy with my ability to cruise 75 - 80 mph in rolling hills prior to changing the gears. The 5:13 ratios cured that. The supercharger really made it fun to drive. If you are evaluating for changing gears reprogram your dash to show the gear you are in while driving under the options menu. It was enlightening to see how much I was running in low gears because I couldn't pull the higher ones. The 5:13's basically gave me an 8 speed instead of a 6 speed. They weren't necessary, but if I had to set up again I'd add the 5:13's and the RIPP immediately with the 37's. Also, as a side note, I really like the rockslide engineering steps.
 

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I went with 4.88 and im pretty happy about it. admittedly my jeep is 95% grocery getter / work transport but I do get off-road a few times a year. I didn't want to lose even more MPGs going to 5.13s since I usually travel on 55mph roads to and from everywhere. The 4.88 certainly will drop down to 7th at times and every once a while into 6th at those speeds when im on a highway going uphill and upwind (it did it yesterday going 70mph on a highway with a steep grade uphill). But isn't that the point? The transmission is supposed to figure out and use the best gear for the condition. I don't want to be in 8th all the time every time. That being said I get it for more dedicated off-roaders.
 

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I went with 4.88 and im pretty happy about it. admittedly my jeep is 95% grocery getter / work transport but I do get off-road a few times a year. I didn't want to lose even more MPGs going to 5.13s since I usually travel on 55mph roads to and from everywhere. The 4.88 certainly will drop down to 7th at times and every once a while into 6th at those speeds when im on a highway going uphill and upwind (it did it yesterday going 70mph on a highway with a steep grade uphill). But isn't that the point? The transmission is supposed to figure out and use the best gear for the condition. I don't want to be in 8th all the time every time. That being said I get it for more dedicated off-roaders.
Changing to taller tires requires lower differential gear ratios to keep the same final drive ratio. We need to know the tire diameter along with the axle ratios to understand the final gearing. My jeep had an easier time at 55 on taller gears than at 70. Good post, everyone's got to set up for their weight, equipment, and intended use.
 

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I am also on BFG KM3 37's with MC 3.5 game changer. Re-geared to 4.88 and am very happy with the result. It has a little better acceleration than the stock Rubicon, same low end torque as stock and very comfortable on the highway without searching for gears.
 

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You’re very smart OP for going right to the 5.13. A 4.88 upgrade from 4.10 is a waste of money with 37’s. Good job
 

azrubi

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I don't understand, why will it last only a year?
Using the stock pumpkins, the ring and pinion gear teeth will be significantly narrower than your stock ratio gears. This equates to a weaker link. Combine that with heavier tires and wheels, and you're setting yourself up for something breaking. You can probably get by with light offroad use...for awhile.
 

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Using the stock pumpkins, the ring and pinion gear teeth will be significantly narrower than your stock ratio gears. This equates to a weaker link. Combine that with heavier tires and wheels, and you're setting yourself up for something breaking. You can probably get by with light offroad use...for awhile.
There’s a lot of people on 37s and bigger who are running 5.13s and wheeling.
 

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Using the stock pumpkins, the ring and pinion gear teeth will be significantly narrower than your stock ratio gears. This equates to a weaker link. Combine that with heavier tires and wheels, and you're setting yourself up for something breaking. You can probably get by with light offroad use...for awhile.
:lipssealed: @Sean K. Have any experience wheelin on 5.13s?
 

No IFS

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What you will find like most things you hear in the media. the experts on 5.13’s don’t have 5.13 Ratio. Have never driven with 513’s. Yet know everything about them. The same people have already reviewed the diesel and so on and so forth. Don’t believe this CNN type fake news BS. Find a friend go for a test drive and you will love 37” with 5.13.
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