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

[wrexdet]

if you are staying with 35's I would spend that 2k somewhere else. 4.56 = very small difference. 4.88 will be more noticeable but you will likely loose mpg. 4.10's with the 8 speed is pretty good.

I wasn't expecting to see this...so 4.10, 3.6L on 35's performs okay both on the hwy and off road? I was fully resigned to the fact that if I wanted to add a lift and bigger tires I would have to regear.

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[Blues Fan 30]

I wasn't expecting to see this...so 4.10, 3.6L on 35's performs okay both on the hwy and off road? I was fully resigned to the fact that if I wanted to add a lift and bigger tires I would have to regear.

Nah you'll be fine tbh. Would the driving experience be better with different gears? Probably yes. Is it worth thousands to do? Probably no. 4.10s and 35s if I recall is actually better than 3.45s and 33s which is what most of us sahara drivers go with and honestly I think mine rides fantastic. You ask about the xtreme package and why jeep went 4.56 and not 4.88 and the answer is probably fuel economy if I had to guess.

 

[ijp4fun]

4:88's
Excavate your garage floor down a few inches.
37's

 

[azjl#3]

While I am a big proponent of regearing in general, I would not regear with 35s on an automatic when you already have 4.10 gears. The transmission is capable of handling that just fine. Save your money for gas on your big trips.

while i voted for 4.88, a new one did grenade on me. Why do regear guys have to look at it again at 500 miles, factory didnt. Oh, mine grenaded, thats why.

I have 35's, in the mountains with 4.1. I notice obvious use of lower gear or two up 7% grades. So what. I notice little difference, to be honest, no real difference starting from a stop. In fact, I think it's not jerky like the 4.88 was. That said, if a few grand falls in my lap, I may go to 4.88 or 5.1

Bottom line, drive the 4.1/35 around first. I'm on month 4, and the more I drive it, the less I am thinking regearing.

 

[grimmjeeper]

I wasn't expecting to see this...so 4.10, 3.6L on 35's performs okay both on the hwy and off road? I was fully resigned to the fact that if I wanted to add a lift and bigger tires I would have to regear.

Whether the 4.10s are good enough for you is always subjective. Some people are fine with them. Some aren't.

Two things factor into that.

1. The automatic transmission is good at covering up a gear-tire mismatch so it's harder to tell if it's good or not.
2. The Rubicon 4:1 transfer case also compensates for mismatched gears.

It's rare for people to say they regretted doing gears to match tires. And half of the people who do regret it went too far (5.13s or 5.38s for 33-34" tires).

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

Best bet if you don't know for sure is to try out the bigger tires without a regear. If the performance is good enough for you, skip the regear. If you don't like the performance, get the regear done.

Personally, I would do 4.56-4.88 with 35s and a 3.6. Leaning towards 4.88 if towing is involved. But 4.10s aren't un-driveable. 3.45s probably would be for me, especially with the 2.72:1 tcase.

 

[AVGeek99]

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?

You must have a short garage. I have 37s with a 3.5" MC GC. I did before and after measurements when I got the lift. I netted 5.4". When I saw it I was worried it wouldn't fit through my standard 7' garage door, but it fits with a few inches to spare.

If you truly can't fit with 37's then either stick with the 4.10s. I have a manual and the 4.10s were acceptable running 35s, the auto will handle it even better. If you feel you really must regear, go to 4.88s. One step up in gears is not worth how much it costs. Then if you end up moving somewhere with a bigger garage you're ready for 37s.

 

[Crowbar]

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?

I have a 23 JLUR XR. Came with 315's (35) and 4.56. The 4.56 were not enough gear for the 35's. Struggled to hold 8th gear at 75mph and the slightest headwind or grade and it'd be dropping to 7th or 6th gear.
I would have got 4.88's when I ordered it but I knew it was going to get 37's and regear to 5.13's.

 

[Zandcwhite]

I have a 23 JLUR XR. Came with 315's (35) and 4.56. The 4.56 were not enough gear for the 35's. Struggled to hold 8th gear at 75mph and the slightest headwind or grade and it'd be dropping to 7th or 6th gear.
I would have got 4.88's when I ordered it but I knew it was going to get 37's and regear to 5.13's.

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.

 

[Robertyoke]

You must have a short garage. I have 37s with a 3.5" MC GC. I did before and after measurements when I got the lift. I netted 5.4". When I saw it I was worried it wouldn't fit through my standard 7' garage door, but it fits with a few inches to spare.

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...?

 

[nU7OuxIx]

This is a dicey question to ask but will anyways.

What's the estimated MPG's with 35's on 4.56 and 4.88? Any real world experience?

I'm wondering if it's a 1 mpg different or a 10 mpg difference.

 

[yokramer]

This is a dicey question to ask but will anyways.

What's the estimated MPG's with 35's on 4.56 and 4.88? Any real world experience?

I'm wondering if it's a 1 mpg different or a 10 mpg difference.

Im running 4.10s on 35s with the 2.0 and get usually 18mph around town, but can see up to 20 if I drive really nice, ususally 20 on the highway up to ~25 if I stick to 65 or below. Replacing gears in the Rubicons is a bit blown out of proportion in the JLs. If youre in a sport yea probably think about doing it but otherwise its a waste of money you could put elsewhere.

 

[StonerSR25]

Thanks for doing this...I'm thinking about getting a jlurx with the 35" tire package.

Why does jeep push the 4.56 ratio while most people so far are saying get 4.88? I would think if 4.88 is the way to go then Jeep would be using that on their 35" tire package.

my guess is they need to meet the fed highway mileage estimates.

 

[Zandcwhite]

my guess is they need to meet the fed highway mileage estimates.

Most people are saying 4.88s because they know odds are if you're regearing a Rubicon you'll eventually end up on 37s. That and a lot of people expect the Jeep to drive like an old 4 speed auto where it gets into top gear and stays there the entire time you're on the highway. 7th is still an overdrive. It's supposed to shift alot. There's no benefit of spinning 3k rpms under light loads downhill on the freeway and it eliminates the entire advantage of having a double overdrive transmission. You're a downshift away from more gearing and more rpms... when you need them. There's no reason to gear so deep that you are out of upshifts by half the speed limit. Non-rubicon owners do just fine on 3.45s and 32s with this transmission, the equivalent of 4.10s and 37s or 4.88s and 45" tall tires. The idea that you need 4.88s for 35s is insanity. You might as well throw in a 700r4 from the 80s as you've ruined the advantages of 2 overdrives entirely.

 

[rcoe]

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.

 

[ijp4fun]

This is a dicey question to ask but will anyways.

What's the estimated MPG's with 35's on 4.56 and 4.88? Any real world experience?

I'm wondering if it's a 1 mpg different or a 10 mpg difference.

V6, Auto, 35's, 4:88's I get between 15-17 mpg.
Just did a 180 mile trip last weekend, 30 miles was in the dirt and between sea level and 6000 ft. When I got home and filled up mpg was 17.1

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