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4.88 or 5.13?

Ricmcd

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I put 4.88s on my JL Moab when I got my 37's last week. It's fantastic and drives like a dream. Still get the same MPG as before and the 8sp happily shifts into all 8 gears on the highway.
I have 37x12.5’s on my 2 door JL Rubicon with the 3.6 and 8 speed auto and am considering this same change to 4.88’s or 5.13’s
I rarely see 7th or 8th gear since the tire change, I would like to drive on the freeway at 75-80 when traveling long trips without winding up the engine. Not sure which is better but 4.88’s seem to be a happy medium
 

Bearded_Dragon

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I put 4.88s on my JL Moab when I got my 37's last week. It's fantastic and drives like a dream. Still get the same MPG as before and the 8sp happily shifts into all 8 gears on the highway.
When you're going 70MPH and punch it, does it shift into 4th gear? Way...A...Life (have to spell it that way because its blocked on this website) reports 8 speed+5.13+37s at 70MPH will not go below 5th gear making it difficult to pass.

Video below for reference.
 

rustyshakelford

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When you're going 70MPH and punch it, does it shift into 4th gear? Way...A...Life (have to spell it that way because its blocked on this website) reports 8 speed+5.13+37s at 70MPH will not go below 5th gear making it difficult to pass.

Video below for reference.
4.88 is really a great combo with 37s and the 8 speed. The manual does great with the 5.13s. If you have aspirations of 38-40s, the 5.13 and auto would be a safe direction

Brett
 

sprayingmango

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When you're going 70MPH and punch it, does it shift into 4th gear? Way...A...Life (have to spell it that way because its blocked on this website) reports 8 speed+5.13+37s at 70MPH will not go below 5th gear making it difficult to pass.

Video below for reference.

I'm still in the break-in period under 500 miles so I have been driving it very gingerly. Once I'm over that I will test this.
 

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sprayingmango

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When you're going 70MPH and punch it, does it shift into 4th gear? Way...A...Life (have to spell it that way because its blocked on this website) reports 8 speed+5.13+37s at 70MPH will not go below 5th gear making it difficult to pass.

Video below for reference.
Just tested this as I am almost at the 500 mile mark. It shifted instantly into 4th! It actually kinda scared me how fast it shifted lol. I was cruising at 70 in 8th. Gave it gas to simulate a pass and it went into 4th and I was flying. 4.88s for the win!!
 

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Just tested this as I am almost at the 500 mile mark. It shifted instantly into 4th! It actually kinda scared me how fast it shifted lol. I was cruising at 70 in 8th. Gave it gas to simulate a pass and it went into 4th and I was flying. 4.88s for the win!!
AWESOME! Appreciate the info, 4.88s will be my choice.
 

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I do not think you are stupid, I agree with everything you said. I too prefer deep gears in my vehicles. I am currently running 5.13's In a JLUR 6 speed with 35's. With two overdrive gears in Jeeps JLs they are still easy to drive on the interstate even with 5.13's. Why not consider 5.38's? cause you know your going to run 37's someday, maybe even 40's, plus gears make for a great foundation for other mods.
How is it with the 5.13's and which vendor did you go with? I have the stock rubicon with 33" and the 6 speed and its a dog but I also live at 6300ft. Considering going 5:13 just for the better performance and 35's next year. 6th gear is unusable and I stay mostly in 4th and sometimes 5th on the highway.
 

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The pinion gear on those 5.13s IS TIIIIINY!

it's not just the size of the teeth, it's how many and how much of each is in contact with the ring gear that determines strength. I'd say that 5.13s are a huge risk. Owning and being obsessed with 4th gen fbodys I am all too familiar with this concept. Failure rate on the 7.5 rears in thsee things is much higher once going to 4.10s, which arequires perfect for a 6 speed ls1 car.

I assume assume all of you guys are rocking Rubicons. I'm a jeep newb. Have to imagine that the loss of strength is significantly amplified when talking about the front 30/35 in my sport. :( Which really stinks for me.
I'm also a 6M BTW and have to say the 3.6 with the 3.xx gears is God awful. No grunt at all down low. It's very dissapointing and I just don't know how these manufacturers put engines suited to smaller, lighter cars in trucks and saddle then saddle them with too small gears. I also know that folks not personally experienced with regearing tend to be scared of driveability of fuel economy when contemplating bigger gears. DON'T BE! We have been brain washed into thinking 2.73s and 1,700 rpm at 65 are the way to go. Wrong. These vehicles are geared to pass archaic fedreal fuel economy standards. Testing procedures have little to do with the reality of actually driving. Sixth gear in my jeep is 100% useless and has only been used MAYBE 10 times for seconds at a time since getting the vehicle last October. The gentle rolling hills of middle/lower NYS mean constantly switching between 4th and 5th gear. It's annoying. I have all but given up on using my door hinge mounted foot peg. (Doors come off and STAY off all spring, summer and fall, regardless of weather). Every time I pop my leg oUT and reSt my foot on it I have to pull my.leg back in so I can downshift while on the highway. 3rd gear gets used a healthy amount on the highway as well. The damn thing just won't go when traffic dips to 50mph on a hill in 4th.

This isn't just a jeep thing. My 2000 5.3 auto Silverado has been manually shifted by me for the majority of its 300k plus miles. Stock drive train, stock tires with the factory 4.10's (I have the holy grail of newer pickups....factory 4.10's and posi in a nicely optioned ttuck) meant constantly downshifting from 4thOD to 3rd on the highway. When I put 35s on it several years ago 4th became as useless as my jeeps sixth. 2nd gear is needed an alarming amount while towing my popup. That 5.3 V8 is gutless just like my jeep. And it literally feels like hitting a nitrous button when it hits 2,800 rpm while towing. At least the jeep isn't a complete on/off switch like my truck, but in also haven't towed with it yet.

Back to big gears. I regeared my truck from 4.10 to 4.88 shorly after putting the 35s on. Every one I talked to about the gears said I was crazy. "4.88s?!?!?!?! Your going to spin 5 grand on the highway!!! You can't put gears that big in it unless it's a racecar." Wrong. It's a simple mathematical equation and I spinning 2,500 rpm at 70mph is perfect. I got the use of my OD back. I was absolutely thrilled within the first 10 seconds of driving the truck with new gears. Within 20 seconds I wished I had gone with 5.13s. Live and learn. But I was also scared about breaking parts. A literal rear end explosion (factory g80 locker) is what prompted the regear. I did it all myself, but had little interest in going back in and dking it again in the event in stripped a gear.

Holy crapolla, sorry for the boriginal novel.

I'm surprised I don't come across used factory 4.10 gear sets often. I know some of you are regearing you're Rubi's. Aren't people selling the stock gears after doing so? While I'd like to go biggest than 4.10 I would also be happy to sAve some money and and buy used factory parts. I sold my trucks 4.10s in a day online and the rear set had nicks from the explosion. And still had people asking me for them months later. SELL ME YOUR JEEP 4.10S. Lol.

Is there a general consensus on a "safe" limit on gear size for my little front end? I'll be installing my 35s shortly. My 6 speed manual which is effectively only a 5 speed is gonna become effectively a 4 speed when I do I'm afraid.

One of the main reason for buying my Jeep was the option of having a manual trans. 2 of my 4 vehicles are manual and they all would be were it possible. Having said that, I'm pretty sure the 8speed auto feels a lot peppier than my manual. The no torque motor combined with smallish gears have been making me second guess having gone with a manual lately.

I need to be quiet and go away now. Thanks to anyone who actually read all of this. ;)
 

ChattVol

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4.88 is really a great combo with 37s and the 8 speed. The manual does great with the 5.13s. If you have aspirations of 38-40s, the 5.13 and auto would be a safe direction

Brett
Have you driven a jl 6 speed with 4.88s to compare to the 5.13s?
 

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Debating between 4.88s and 5.13s in a 3.6 auto with 37's. Sounds like people have done both and are happy. Is there a right answer? If i've never driven a stock JLUR on 4.10's, is 5.13 going to be a huge jump?
 

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Debating between 4.88s and 5.13s in a 3.6 auto with 37's. Sounds like people have done both and are happy. Is there a right answer? If i've never driven a stock JLUR on 4.10's, is 5.13 going to be a huge jump?
I'd like to know also. Watching
 

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Debating between 4.88s and 5.13s in a 3.6 auto with 37's. Sounds like people have done both and are happy. Is there a right answer? If i've never driven a stock JLUR on 4.10's, is 5.13 going to be a huge jump?
I probably mentioned it already in this thread, but no one has ever installed 5.13s and wished they'd gone with 4.88s....but many with 4.88s wished they'd gone with 5.13s.
 

Halstem1

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I probably mentioned it already in this thread, but no one has ever installed 5.13s and wished they'd gone with 4.88s....but many with 4.88s wished they'd gone with 5.13s.
Oh man. For real? That's kinda what I'm wondering. I was dead set on 4.88's because its a daily driver and honestly I don't hate the 4.10's. But everyone is boasting the 5.13's. And with just buying a travel trailer, I feel that extra low end power would be super nice.
 

2Wheel-Lee

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Oh man. For real? That's kinda what I'm wondering. I was dead set on 4.88's because its a daily driver and honestly I don't hate the 4.10's. But everyone is boasting the 5.13's. And with just buying a travel trailer, I feel that extra low end power would be super nice.
Don't get too hung up on people telling you what the math indicates. That math doesn't take into consideration the weight of the heavier 37" wheels and tires (especially if you're running beadlocks), nor does it factor in the increased rolling resistance of common aggressive tread. And then there's the reduced aerodynamics of wider/taller tires and increased exposure of the rear of the rear fenderwells with lifts and larger tires.

And if you're going to be pulling a trailer, I think you know might know what's best for you.
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