4:88s, not so popular, but gonna try it

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13_gecko_rubi

New member
I will continue to say for 37s if you are going to regear you want 5.13s not 4.88s. With the Rubicon axles due to size issues now. I now know a dozen or so people that have regeared them for 37s. About half went 4.88 and said they wished they had done the 5.13s like I told them. Most of the guys that did 5.13s are happy but a few wish they had gone even to 5.38 because they still drop out or 8th a lot.

I think 5.38 I'd be worried about the pinion size too but too early to tell.

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silverbullet88

New member
13_gecko_rubi said:
I will continue to say for 37s if you are going to regear you want 5.13s not 4.88s. With the Rubicon axles due to size issues now. I now know a dozen or so people that have regeared them for 37s. About half went 4.88 and said they wished they had done the 5.13s like I told them. Most of the guys that did 5.13s are happy but a few wish they had gone even to 5.38 because they still drop out or 8th a lot.

I think 5.38 I'd be worried about the pinion size too but too early to tell.

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In the JLX video one of the guys break a 5.38 ring and pinion. But that was in a stock rubi axle on 40’s! Lol. And he was pointed downhill off a gnarly looking ledge/ obstacle. Broke when he tried to reverse up it..so the weaker side of the gears.
 

wayoflife

wayoflife

Administrator
Staff member
13_gecko_rubi said:
I will continue to say for 37s if you are going to regear you want 5.13s not 4.88s. With the Rubicon axles due to size issues now. I now know a dozen or so people that have regeared them for 37s. About half went 4.88 and said they wished they had done the 5.13s like I told them. Most of the guys that did 5.13s are happy but a few wish they had gone even to 5.38 because they still drop out or 8th a lot.

I think 5.38 I'd be worried about the pinion size too but too early to tell.

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What I LOVE about 5.13's on 37's is the power you get off the line. What I'm not so fond of is the loss in MPG. I spend a LOT of time on the road and typically at speeds of 80 MPH and I have seen a measurable reduction. The other thing I don't like about 5.13 is passing at high speeds. Sure, I can get 7th and 8th again but I can't get it to drop into 4th (even manually shifting it) where the real power is or at least, not unless I slow up to about 60-65 mph first. With 4.10's, you're always running in 5th and 6th and when you need the get up and go, the transmission will dig into 4th and get you moving.

Having seen a 5.38, there's no way I'd run them in a factory axle especially being so much of the wheeling that I do is so far from anything. Maybe if all I had to play in were parks and trailered my Jeep there.
 

wayoflife

wayoflife

Administrator
Staff member
silverbullet88 said:
In the JLX video one of the guys break a 5.38 ring and pinion. But that was in a stock rubi axle on 40’s! Lol. And he was pointed downhill off a gnarly looking ledge/ obstacle. Broke when he tried to reverse up it..so the weaker side of the gears.
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LOL!! Oh yeah, 5.38 is the right ratio for 40's but not the smartest thing to run in a factory axle and with tires of that size.
 

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13_gecko_rubi

New member
wayoflife said:
What I LOVE about 5.13's on 37's is the power you get off the line. What I'm not so fond of is the loss in MPG. I spend a LOT of time on the road and typically at speeds of 80 MPH and I have seen a measurable reduction. The other thing I don't like about 5.13 is passing at high speeds. Sure, I can get 7th and 8th again but I can't get it to drop into 4th where the real power is or at least, not unless I slow up to about 60-65 mph first. With 4.10's, you're always running in 5th and 6th and when you need the get up and go, the transmission will dig into 4th and get you moving.

Having seen a 5.38, there's no way I'd run them in a factory axle especially being so much of the wheeling that I do is so far from anything. Maybe if all I had to play in were parks and trailered my Jeep there.
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Ya the 5.38 looks tiny! You are getting worse mpg? That's odd, i would have expected better holding 8th more. The 8 speed is still a learning game on what's best. Only time will tell. Thanks for the feedback!!!

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wayoflife

wayoflife

Administrator
Staff member
13_gecko_rubi said:
Ya the 5.38 looks tiny! You are getting worse mpg? That's odd, i would have expected better holding 8th more. The 8 speed is still a learning game on what's best. Only time will tell. Thanks for the feedback!!!

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Yup, I'm now seeing about 3 MPG less on average on the highway.
 

wayoflife

wayoflife

Administrator
Staff member
13_gecko_rubi said:
Holy hell!! Well you can probably blame me, I'm sorry. I'm pretty sure that's what I recommended to Jim for folks. Not for yours specifically but in general. :-(

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:cheesy: It's all good. Not like any of the Jeeps I've ever owned got good MPG. I think the JL was the first to shock the hell out of me with how far it would take me on a tank of gas, even with 37's. Now, it's closer to what my other Jeeps get or have gotten :crazyeyes:
 

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13_gecko_rubi

New member
wayoflife said:
:cheesy: It's all good. Not like any of the Jeeps I've ever owned got good MPG. I think the JL was the first to shock the hell out of me with how far it would take me on a tank of gas, even with 37's. Now, it's closer to what my other Jeeps get or have gotten :crazyeyes:
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I'll send ya my stock Rubicon axles and send me your current axles. I'm only offering to help you out :)

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wayoflife

wayoflife

Administrator
Staff member
13_gecko_rubi said:
I'll send ya my stock Rubicon axles and send me your current axles. I'm only offering to help you out :)

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How sweet of you :eek:

To be fair, my MPG isn't exactly horrible. It's just that I could easily average 14-16 mpg before and that's close to a 300 mile range! Now, I'm seeing more like 11-13 mpg which is more what I'm used to with 37's or at least, on a JK.
 

notnalc68

notnalc68

That dude from Mississippi
wayoflife said:
What I LOVE about 5.13's on 37's is the power you get off the line. What I'm not so fond of is the loss in MPG. I spend a LOT of time on the road and typically at speeds of 80 MPH and I have seen a measurable reduction. The other thing I don't like about 5.13 is passing at high speeds. Sure, I can get 7th and 8th again but I can't get it to drop into 4th (even manually shifting it) where the real power is or at least, not unless I slow up to about 60-65 mph first. With 4.10's, you're always running in 5th and 6th and when you need the get up and go, the transmission will dig into 4th and get you moving.

Having seen a 5.38, there's no way I'd run them in a factory axle especially being so much of the wheeling that I do is so far from anything. Maybe if all I had to play in were parks and trailered my Jeep there.
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Good information. It’s nice to get that insight.


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silverbullet88

New member
wayoflife said:
How sweet of you :eek:

To be fair, my MPG isn't exactly horrible. It's just that I could easily average 14-16 mpg before and that's close to a 300 mile range! Now, I'm seeing more like 11-13 mpg which is more what I'm used to with 37's or at least, on a JK.
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I just did my first fill up with my 37’s and 5.13’s. 15.1 mpg by hand calculation. Tires and gears set by the tazer. I had done about 214 miles and the gas light wasn’t on yet.

I do have the 6 speed and that was 90% city driving but I baby it and go the speed limit lol. If I were to drive up to Tahoe I’d for sure be the 12 mpg range.

I also realized today I need an atlas or a rubi case. Even with the 5.13’s it’s just not low enough.
 

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bluegrassjlu

Member
This is why I like this forum. I got more real world info on this topic than I could find looking anywhere else that's JL specific. We have to travel a lot of highway to get to our wheeling places, and we've been debating on 4.88 vs 5.13. Now I know that the 4.88s will work great.
 

wayoflife

wayoflife

Administrator
Staff member
bluegrassjlu said:
This is why I like this forum. I got more real world info on this topic than I could find looking anywhere else that's JL specific. We have to travel a lot of highway to get to our wheeling places, and we've been debating on 4.88 vs 5.13. Now I know that the 4.88s will work great.
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With 37's and an 8-speed auto, I'd say it's a good compromise. You get more power but without too much of an mpg penalty.
 

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OBJLU

New member
wayoflife said:
What size tires are you planning to run?
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Doh, haha sorry an incomplete thought. Eventually I am going to run 37’s, perhaps 38’s but no bigger, I am on 35’s now but want to take care of the regear first. I plan to put up with the overbearing until I get the new tires.
 

wayoflife

wayoflife

Administrator
Staff member
OBJLU said:
Doh, haha sorry an incomplete thought. Eventually I am going to run 37’s, perhaps 38’s but no bigger, I am on 35’s now but want to take care of the regear first. I plan to put up with the overbearing until I get the new tires.
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Okay, I suppose it depends on how much highway time you spend and whether or not you care about MPG. A 6-speed has lower gearing to begin with so even with 37's, I think you'd find 4.88 to be a good match for them especially being that it may take a bit to get there. 5.13's will give you more power off the line and a better crawl on the rocks but you will burn through gas at highway speeds.
 

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