37's on a Rubicon...

[conFUcius]

Again, most if the factory gearing is just ok. The manual non-rubicon hearing from the factory is atrocious. Borderline criminal. There’s also another huge piece to the puzzle; transfer case gearing. If you’re on 4.10 gears with the 2.0 or diesel you could easily live with the factory gearing and 35” tires. Rolling mass plays a huge roll as well. It’s not as simple as the gear calculators would have you think. There are way too many variables.

Definitely a lot of variables that come into play. Just think that OP (or anyone for that matter) should at least drive a re-geared Jeep before rendering a decision. Money is certainly a limit and I would agree that 35s on 4.10 gearing isn’t worth it but to go to 37s definitely is…

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[word302]

Definitely a lot of variables that come into play. Just think that OP (or anyone for that matter) should at least drive a re-geared Jeep before rendering a decision. Money is certainly a limit and I would agree that 35s on 4.10 gearing isn’t worth it but to go to 37s definitely is…

I don’t disagree but sometimes ignorance is bliss.

 

[Zandcwhite]

If you want the Jeep to feel ‘stock’ with all that stuff… then, yes. If you don’t, then no. At the end of the day, we’re all biased to justify why we mod (or don’t mod) the Jeeps the way we do (or don’t) - few are willing to admit it was a waste of money to buy certain mods.

Have you driven a Jeep that’s been re-geared to bring the gear ratio close to the feel from factory? If so, and you say it’s not worth it, good for you. Most people don’t and just try to justify to themself not to spend the money and think they can get by without having not even tried it… I’m just letting OP know that.

We've owned a dozen different Jeeps, geared anywhere from 3.21 to 5.38 over the years. I've probably driven 2 dozen more. In any other auto, absolutely 4.10's are too tall for 38's. The beauty of this trans is 1st is so low and 8th is so high we can run whichever gearing we want. Quick off the line is fun, but I tend to drive fast for long periods of time. Fortunately the JL is comfortable and handles well enough that that happens quite often. I'll take the trade off.

 

[Zandcwhite]

I believe the formula is [(Desired Tire Size)(OEM Gear Ratio)]/(OEM Tire Size) to preserve the OEM ‘feel’ from factory… not sure how many people follow the straight percentages you stated.

Not to beat the dead horse, but that formula is just Converting current gear Ratio to a % of tire size and then multiplying it by new tire size to get the new gear ratio. Beyond that, if you do that math from a stock sport (3.45/31.47”)*37 you get…4.05 as the desired gear ratio for 37’s. The extra .05 of my stock 4.10’s puts me back to oem non-rubicon gearing on 37’s, no wonder it drives so well? I guess we’ve been “properly geared” all along?.

 

[conFUcius]

Not to beat the dead horse, but that formula is just Converting current gear Ratio to a % of tire size and then multiplying it by new tire size to get the new gear ratio. Beyond that, if you do that math from a stock sport (3.45/31.47”)*37 you get…4.05 as the desired gear ratio for 37’s. The extra .05 of my stock 4.10’s puts me back to oem non-rubicon gearing on 37’s, no wonder it drives so well? I guess we’ve been “properly geared” all along?.

So…you essentially ‘pre-paid’ for gearing for 37s by buying a Rubicon with 4.10 gearing? I think that negates the purpose but… to each his/her own. I’m glad you have extensive experience with Jeeps (this is my second - I started with a JKU 6-speed) and took the time to drive a JLU with an 8-speed re-geared to maintain the stock feel. My point is that most don’t have the experience nor take the time to do it. They just speak out of ignorance, as @word302 put it.

 

[Zandcwhite]

So…you essentially ‘pre-paid’ for gearing for 37s by buying a Rubicon with 4.10 gearing? I think that negates the purpose but… to each his/her own. I’m glad you have extensive experience with Jeeps (this is my second - I started with a JKU 6-speed) and took the time to drive a JLU with an 8-speed re-geared to maintain the stock feel. My point is that most don’t have the experience nor take the time to do it. They just speak out of ignorance, as @word302 put it.

I agree completely, but that happens on both sides of the argument. A lot of opinions get stated as facts. Assumptions get made that people lack experience or knowledge simply because they disagree with your preferred "facts". That's why I take the time to break down the math so that people see there really are 2 sides to it.

 

[landshark99]

I agree completely, but that happens on both sides of the argument. A lot of opinions get stated as facts. Assumptions get made that people lack experience or knowledge simply because they disagree with your preferred "facts". That's why I take the time to break down the math so that people see there really are 2 sides to it.

you are assuming that the sport is the proper standard on which to establish a base, if you use the same formula with a stock rubicon it would say that the right ratio is 4.10/32.8*37=4.62. I run my 37s with 4.88, is it the only answer no, but I prefer the way the Jeep drives both on and offroad with that setup, to each his own

 

[BeachPilot74]

I bought Yukon 4:88s from Northridge4X4 with the forum discount. @@$700 for a complete set with master rebuild kit, with the full intention of a self install. I bought about $300 worth of specialty tools for the the job and studied every video on gear swapping. I planned to tackle it right after retirement in 2019. We had some family issues and we moved to another State. Everything was pushed back. There was no rush, because the auto was fine pushing me forward with 7 out of 8 gears. After a couple of years into retirement, with the mentality of "is my time worth the money saved?", I decided to ask around for the cost of a regear. I got a quote for $800 and had them do it. I have some regret, since they wouldn't warranty the install because I brought them the parts, but I could fix anything if it werent botched too bad. I've changed out a few seals in the last few months, but was okay with that. The wear pattern is spot on when I changed out the gear oil and I'm back to about 16mpgs with my heavy foot.

What is this Northridge Discount? How do you get it.?

 

[Zandcwhite]

you are assuming that the sport is the proper standard on which to establish a base, if you use the same formula with a stock rubicon it would say that the right ratio is 4.10/32.8*37=4.62. I run my 37s with 4.88, is it the only answer no, but I prefer the way the Jeep drives both on and offroad with that setup, to each his own

If you read back through my other posts, I'm well aware. Like I've said, if you prefer quicker off the line, gear down. If you prefer the way the sport drives at freeway+ speeds, 4.10's are more than adequate. With the 4-1 transfer case, crawl ratio is great either way. We roadtrip our jlur thousands of miles every year at 80+mph, so I'm sticking with my higher gearing. Not because I've never driven a Jeep with lower gears, not out of ignorance, not because I can't afford to regear, but because they work great for my use case of this jeep in particular.

 

[19 JLUR Bright Whit3]

What is this Northridge Discount? How do you get it.?

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[Northridge4x4]

What is this Northridge Discount? How do you get it.?

Use discount code "jlwranglerforums"

 

[BeachPilot74]

Use discount code "jlwranglerforums"

Thanks Guys! ?

 

[RidgeRider]

As a regearing skeptic I ran 37s with my 2.0 4cyl 8spd w/o regearing for a year doing lots of gnarly trails in Utah and Colorado. Only issue was some hesitation three times starting from a dead stop on super steep slopes especially in reverse (which is higher than 1st) - otherwise no power issues on or off road.

Because of this hesitation and seeing the new Rubicon w/37s rollover on Potato Salad Hill in Moab, I decided to go with 4.88 gearing and was very surprised at the positive difference it has made. Drives much better on and off road, the engine seems more relaxed and I gained about 2mpg in fuel economy which increases my range. I got 8th gear before regearing as long as I was above 60mph on flat to downhill grades but now it will show up at 50mph or less even going up a mild grade. I guess this shouldn't be surprising since going from 4.10 to 4.88 is nearly a 20% effective gear reduction which is quite a bit. Still a judgement call to spend over $3k to install Dana gears, Dana chromaloy axle upgrades (the labor for this is free with regearing) and in my case I added RCV CV axles in front to improve 4-Lo turning capability with lockers on which added $500 to the bill (and don't forget the mandatory differential oil change after your first 500 miles).

 

[BADBREW]

I'm sure I'll get the "use the search" response, but I did and didn't find a definitive answer. If I put 37x12.5x17's on my 2021 Rubicon, do I need to regear or not? I'm thinking "no" that 4.11's are fine and 4.88's are better, but I just want to know is regearing an immediate need if going from 35's to 37s?

Currently driving a 2020 Rubicon JLU on 37x12.50x17 Trail Grappler shoes with stock 4.10s… I’ve not had any problems. Moving to 4.88 gears as an “immediate need”… No. You may not see eighth gear unless you’re on a level grade with a tailwind., but it’s not been an issue for me. Right now it’s mostly trails and pavement. Once I start doing more overlanding and rocks, I will move to 4.88s, but axles and other items will also drive that move too. Hope this helps.

 

[Patsloft]

I'm sure I'll get the "use the search" response, but I did and didn't find a definitive answer. If I put 37x12.5x17's on my 2021 Rubicon, do I need to regear or not? I'm thinking "no" that 4.11's are fine and 4.88's are better, but I just want to know is regearing an immediate need if going from 35's to 37s?

As an actual guy who has a JLUR with 37s for over a year and had 35s on it before. Yes you should ReGear to 4.88s Your Jeep will be much happier with these gears. Your gas mileage will be better Your engine and tranny will not have to work as hard.

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