Another 4.56 vs 4.88 Thread... Yeah... I'm that guy.

[shane h.]

I was thinking the same thing, you must have one short azz garage.
37's with 3.5 RK lift fits in a 7 foot door with room to spare, like 3-4 inches.
To the Op are you trying to stick your jeep in a tool shed...?

Not a tool shed, but the door is short. And I keep a rack rails on the hard top to carry camping gear and paddle boards.

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[Zandcwhite]

I think it was around for so long with the JK's where re gearing was really needed with 35's. My JK was marginal with 35's and 37's were awful with 4.10's. I went to 4.88's within a month of having 37's.

I had already figured on doing 4.88's again with the JL, but with the 2.0t and 8 speed I really don't see the need.

The JK auto had a 3.59 1st gear after 2012, the early JK had a 2.86 1st gear. The late model JK needed 5.38 axle gears just to match the 8 speed with 4.10s. The early JKs needed 6.74 axle gears... which don't even exist. This transmission has such a low 1st gear that regearing really isn't necessary for a Rubicon until you hit 40"+, at which point you should have ordered your 1 ton axles with deeper gears.

 

[Steph1]

Was going to vote for 4.56 which are perfect for the 35s, but knowing most people can’t stop moving to larger tires, I voted 4.88 in case you eventually move up to 37s.

 

[AC77]

I don’t have any gear upgrade. I own a 22 Sahara diesel stock 3.75. Would 4:10’s give a bit more toque from the line and still keep daily driveability decent ?

 

[grimmjeeper]

I don’t have any gear upgrade. I own a 22 Sahara diesel stock 3.75. Would 4:10’s give a bit more toque from the line and still keep daily driveability decent ?

The diesel is a completely different engine than the 3.6 in some pretty fundamental ways. The gearing needs between the two don't translate at all.

 

[RubiconJL392]

5.13's..with v6, 8speed auto and 35's. I run 4.88's with 392, 8speed and 35's and love it. Especially if you might tow something AND you currently don't like how it is geared now. Hands down 5.13's is my recommendation.

 

[AVGeek99]

Optimal diff ratio is heavily dependent on the transmission you have. Many people, myself included, recommending 4.88s (or shorter) for 37s have the manual transmission.

The automatic can handle can handle bigger tires without regearing because it has two extra gears, is programmed extremely well, and shifts very smoothly. Most of the time the only way to notice it shifting is by watching the tach.

With the manual all that extra shifting gets old quick when going up and down hills constantly. Plus, in the mountains there are times when you need to drop all the way to 3rd, just to maintain speed; that's with 4.88s on 37s. If I had it to do over I would have ordered an auto instead of a 6MT.

 

[Jeep Wick]

Here is the situation:

• 2019 JLUR - 4.10 stock gears
• 8 speed auto
• 3.6 v6
• 2.5" MC GC lift
• 35x12.5R17 MT BB ATs. 37s are off the table for the simple reason that the Jeep on 37s' will not fit in the garage, and my Jeep lives in the garage.
• Steel front bumper with winch to come (+75 pounds or so)
• Will be adding CavFab rear steel bumper and CavFab tire carrier in the near future (+120 pounds or so)
• Spend a lot of highway miles getting to the fun stuff
• Will probably end up towing some sort of small trailer after retirement in the couple years. Goal is to drive to Prudhoe Bay, AK, and see all the stuff between here and there along the way. And there's A LOT of stuff to see.

I do not love the Jeep at its current gearing on the 35s. Re-gear is coming. I'd love to hear from those who are running 35s on the 3.6v6/8spd auto pairing as to which gears you went to if you re-geared. Do you love it? Would you do it differently?

Mine is factory 35 and 4.56 with the V6/8spd... It's a good setup but if given the choice I would have picked 4.88 absolutely. 7th and 8th gear could be more usable.

 

[MA Joop]

It's not a wide ratio 3-4 speed from the 80s. It's not struggling to hold 8th because it's not supposed to. 7th is still overdrive. Gearing it so low that it turns 3k rpms in 8th gear downhill at freeway speed defeats the point of having 2 overdrives. We made the mistake of gearing too low on our 2019 JLUR because I listened to the "you'll never regret gearing lower than you think you need" crowd. 5.38s and 38s was terrible pretty much everywhere. It was in 8th gear at any speed over 40mph, which would be done if it were a 10 speed. There's no point of gearing so low that you're out of shifts by half the speed limit. It lost 2mpg on the freeway as a result. It lost .5 second 0-60 as it had to shift 1 extra time to get there. Even crawling in 4LO was worse with the 100-1 crawl ratio as 1st gear was nearly useless. Even geared too tall with 4.10s and 38s the jeep was better all around. If you like a bunch of rpms going downhill under no load, save $2-3k and simply downshift.

I posted a picture a while back in on of the many other threads on this topic, with my factory 4.88 and 315/70-17s at 80 mph in 8th gear you’re at 2,500 rpm. You’d have to really be moving to be at 3,000 rpm In 8th gear.

Agree to disagree on the crawl ratio, I personally love to use 1st gear in 4-low for either crawling down steep rocky grades or crawling up large rocks. Foot off the gas, it crawls at a walking pace up pretty large obstacles and since you're not adding throttle it generally will walk up without breaking traction.

While I agree that 4.56 and even 4.10 are probably perfectly adequate, for jeep stuff the 4.88s are better in my opinion.

 

[Tncdrew]

Many people who get a chance to drive a properly geared Jeep wonder why they didn't regear sooner.

This comment says it all perfectly!

 

[Zandcwhite]

I posted a picture a while back in on of the many other threads on this topic, with my factory 4.88 and 315/70-17s at 80 mph in 8th gear you’re at 2,500 rpm. You’d have to really be moving to be at 3,000 rpm In 8th gear.

Agree to disagree on the crawl ratio, I personally love to use 1st gear in 4-low for either crawling down steep rocky grades or crawling up large rocks. Foot off the gas, it crawls at a walking pace up pretty large obstacles and since you're not adding throttle it generally will walk up without breaking traction.

While I agree that 4.56 and even 4.10 are probably perfectly adequate, for jeep stuff the 4.88s are better in my opinion.

At 85mph that's 2700+ and at 90mph it's just under 2900rpms. Technically not 3k but closer than I want to be downhill with no load. A properly geared (since you overgeared types like to use the term like your way is the right way) stock rubicon will be closer to 2500rpm in the same scenario, fully utilizing the double overdrive to run low rpms at light loads. That's the true greatness of this transmission though. 1st gear is low enough to run taller than "proper" and the 2 overdrives are tall enough to run deeper than "proper". As someone who lives out west and sets the cruise control at 85mph regularly I prefer to save 400 rpms when I can and from experience it makes a large difference on those roadtrips. 400 rpm didn't sound like much, but when it's hours at a time it adds up. For my use 4.56 was perfect for 37s. Too each there own.

 

[jbcrane]

...I do not love the Jeep at its current gearing on the 35s. Re-gear is coming. I'd love to hear from those who are running 35s on the 3.6v6/8spd auto pairing as to which gears you went to if you re-geared. Do you love it? Would you do it differently?

4.88's.
Those MTBB's are a 71# tire so depending on your wheels you're around 100#/corner. Especially if you tow, with a loaded rig on long trips, you'll be glad you went with the 4.88's.
I'm running 4.88's and 315's on a MT Sport in Colorado. He feels spry with plenty of power at altitude. My next set of tires will be heavier than the current 62# KO2's and I'll not fret one bit over that.

 

[Pismo61]

Go one step higher than you think.4.88s is only 7% more rpm.

 

[Jtphoto]

4.56 is the perfect gear for 35s. 4.88 for 37s.
So as mentioned 4.10 to 4.56 is not a big change and I’m not sure you would even be happy with that. so for you and your situation you may be just better off with 4.88.

 

[Old Dogger]

For the heavier JLU, 4.88'S, JL, 4.56.

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