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4.88 or 5.13 w/37”?

FLUndertaker

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I am out of time and need to make a decision, the more I read the more I succumb to analysis paralysis.
Running 37” ridge grapplers with 3.6 and auto trans. Currently about 1500’ above sea level with trips in the future to Colorado and utah hopefully. Very rare towing but occasionally my CJ7 on a car hauler. Not a daily driver but weekend toy and bug out vehicle only.
4.88 or 5.13 ???
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Krobarr

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I've bought 5.13's and have yet to install them. I did a lot of research and asked a lot of people that I felt had an opinion worth hearing. Bubba form Exodus said it best though,"I hear people all the time saying I wish I went bigger(4.55vs 4.10, 4.88 vs 4.55, 5.13 vs 4.88), but have never heard anyone say they wish they'd gone smaller!
Additionally Trail recon did a YouTube vid a year ago about real time install and recently did a recap after almost a year with the gears(5.13's). Lastly, you can go to 40's with %.13's if you ever decided too, definitely truss up if you do though, or buy Dana 60's with the right gearing already!
 

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I run 5:13 gears with 37's in my 2 door JK 6 speed and it's perfect here at sea level. If I was at a higher elevation, or had to battle hills I deffinately wouldn't go numerically lower.
 

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KurtP

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I've bought 5.13's and have yet to install them. I did a lot of research and asked a lot of people that I felt had an opinion worth hearing. Bubba form Exodus said it best though,"I hear people all the time saying I wish I went bigger(4.55vs 4.10, 4.88 vs 4.55, 5.13 vs 4.88), but have never heard anyone say they wish they'd gone smaller!
Additionally Trail recon did a YouTube vid a year ago about real time install and recently did a recap after almost a year with the gears(5.13's). Lastly, you can go to 40's with %.13's if you ever decided too, definitely truss up if you do though, or buy Dana 60's with the right gearing already!
TR went down to 4.88 and said it was better.

i usually agree with “you cant go to low”, but decided after much deliberation and consideration of pinion head sizes to go with 4.88.
 
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Went with 4:88 at sea level...couldn’t be happier with the 37s it should come with these from the factory...I would recommend doing it even if your running 35s
 

Jaydebe

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I'm new to this, so my word is just my experience.
I have 25k on the odometer in 7 months.

I've used the JTR in a lot of ways; towed from West Coast to East Coast (all stock)
37s from about 9k to 25k, loaded with rack, tent, bikes and overland gear. Cross country trips, I live at just under 5k' in the mountains, I'm always going up, down or turning.

The 37s were fine in stock form (Tazer Installed) with just a tonneau and bikes on the highway, often still pulling out 18ish mpg and able to keep 8th gear on the highway.

As I loaded it down more, keeping it in 8th was harder and harder. Our last trip to Az.; we avg. 12.9mpg over 5,000 ish miles. It was loaded down and the truck felt it. It would go into 8th once in a while, but typically 7th and 6th under high winds, 80+mph, etc.

Off-Roading, in 4L, it still crawled on trails like Broken Arrow (I was surprised), but the tranny really seems to be able to absorb the use of 37s pretty well with use of a Tazer.

I'm 90% sure that just a few hundred RPMs of going 4.88 is where it's at. Any time I manually placed it in 8th and moved back to auto; it stayed and mpg climbed a little. I truly think it just needs just a little more RPMs to get back better use of 7 & 8th to gain 3ish mpg and drivability.

This is all IMO.
Being new to all of this, I think I'm being 100% objective here. Plus, If I decide to go to 35's for any reason, I think I'll be better off and not having to regear yet again.

Gear brand is my question. Is Nitro worth 2x the $?
 

morejeepsthanicancount

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Should I re-gear when moving to 37s, I'll be doing 4.88s. I've driven a buddies Rubi on 5.38s and 40s and it was geared way too low for my liking. I do a lot of long hwy trips with the family, beach, mountains, etc and 4.88s will be where I end up to retain some fuel mileage and to hold 8th at higher speeds. The 8 speed is much different from any other trans I've had in a jeep before. Due to all the "extra" gears above my 5 and 6 speeds, I think 4.88 will be perfect for those who care about fuel economy, and just let the 4Lo and tranny handle crawling just fine.
 
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FLUndertaker

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Should I re-gear when moving to 37s, I'll be doing 4.88s. I've driven a buddies Rubi on 5.38s and 40s and it was geared way too low for my liking. I do a lot of long hwy trips with the family, beach, mountains, etc and 4.88s will be where I end up to retain some fuel mileage and to hold 8th at higher speeds. The 8 speed is much different from any other trans I've had in a jeep before. Due to all the "extra" gears above my 5 and 6 speeds, I think 4.88 will be perfect for those who care about fuel economy, and just let the 4Lo and tranny handle crawling just fine.
Rubicon? 4:1 lo range.
 

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FLUndertaker

FLUndertaker

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What would the RPM differences be for an 8 Spd auto with 37’s (36.25” actual) between the 4.88 and the 5.13 ratios at say 75-80 mph?
 

Andrew05LJR

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Just tossed in 488s, with 37s it'll be close to a rubicon gearing with factory tires. Its perfect if you like highway driving and even better if you do a mix like I do.
 
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FLUndertaker

FLUndertaker

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Just tossed in 488s, with 37s it'll be close to a rubicon gearing with factory tires. Its perfect if you like highway driving and even better if you do a mix like I do.
So pretty much like 4.10 with factory 33”?
 

Russler

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May not be helpful but I am going w/ dealership installed Mopar 4:88's so they dont hassle me on any warranty issues. Ultimately will mitigate any need to throat punch a service advisor...win/win all the way around :blush::blush:
 

jc1986

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May not be helpful but I am going w/ dealership installed Mopar 4:88's so they dont hassle me on any warranty issues. Ultimately will mitigate any need to throat punch a service advisor...win/win all the way around :blush::blush:
I would be interested in hear how that goes. I’m contemplating doing the same in the spring.
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