Rubicon Running 37's

I have to say, I'm super impressed how well a stock JL Rubicon does with 37's. It was only about a year ago that I was running 37's on my JK and I remember when I first got them on, how awful it drove. It felt sluggish and I didn't feel safe with factory brakes. Fast forward a year and I just put 37's on my new JL and it drives so much better. Still feels like it wanders on the freeway but that just comes with the territory. Not sure Jeep will ever fix that. But, as far as power and braking...so much better.

The only thing I may change (other than adding a 2.5" Enforcer lift this week) is gearing. I'm curious how many of you with 37's have re-geared vs leaving the 4.10's. This issue isn't low end for me, it's more the lack of 8th gear on the freeway. Not a huge deal but something I'll definitely deal with at some point.

I have been happy with the 4.10 and 37" tires and currently don't plan to re-gear, but I have many times thought about 4.88 gears if I ever did. I'm just not sure I care that I now only see 8th gear on the downhill sections. I still drive my TJ around as much as my JL, and in that, I never get past 4th gear. LOL

LOL! I just posted this on another thread but thought you might find it useful as well.


Of course, this is just my opinion. :yup:

Thanks Eddie. Saw that after I posted this. Actually, it came up in a Google search but didn’t come up in a forum search.

I’m thinking 4.56 but that’s a lot of money for such a small difference. Wish we could tune shift points with a handheld tuner.


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SLO said:

Thanks Eddie. Saw that after I posted this. Actually, it came up in a Google search but didn’t come up in a forum search.

I’m thinking 4.56 but that’s a lot of money for such a small difference. Wish we could tune shift points with a handheld tuner.

Click to expand...

Oh yeah, 4.56 would be a waste if you ask me. I'd go 4.88 at bare minimum or nothing at all.

SLO said:

I have to say, I'm super impressed how well a stock JL Rubicon does with 37's. It was only about a year ago that I was running 37's on my JK and I remember when I first got them on, how awful it drove. It felt sluggish and I didn't feel safe with factory brakes. Fast forward a year and I just put 37's on my new JL and it drives so much better. Still feels like it wanders on the freeway but that just comes with the territory. Not sure Jeep will ever fix that. But, as far as power and braking...so much better.

The only thing I may change (other than adding a 2.5" Enforcer lift this week) is gearing. I'm curious how many of you with 37's have re-geared vs leaving the 4.10's. This issue isn't low end for me, it's more the lack of 8th gear on the freeway. Not a huge deal but something I'll definitely deal with at some point.

Click to expand...

For whatever it's worth I will put my 2cents in.

I have Cooper 12.50x37s on our JLUR and feel that the 4.10 gearing is perfect for a daily driver thanks to the amazing 8 speed auto.
We live on the northeast edge of the Phx metro area in hilly AZ and have zero problems with gears on flat ground or hills. I do not wheel the Jeep, we have a nicely built up Rzr for that, and I can see re-gearing to 5.13 for hardcore off-roading but I cannot understand re-gearing for a daily driver.

Our JL always runs in 8th on flat ground and downhills - I say so what if it stays in 7th or 6th on moderate uphills and we have plenty of that around here? We get decent gas mileage with the 4.10 gears, if we geared lower the engine would run at higher revs all the time and reduce gas mileage. Why would you want that? What is the actual problem with running in 6th or 7th going uphill? The terrific 8 speed trans keeps the revs right in the sweet spot on our Jeep. I sure don't see any issues.

Again, if I was a serious wheeler like Eddie, I would be running 5.13s.

SLO said:

I have to say, I'm super impressed how well a stock JL Rubicon does with 37's. It was only about a year ago that I was running 37's on my JK and I remember when I first got them on, how awful it drove. It felt sluggish and I didn't feel safe with factory brakes. Fast forward a year and I just put 37's on my new JL and it drives so much better. Still feels like it wanders on the freeway but that just comes with the territory. Not sure Jeep will ever fix that. But, as far as power and braking...so much better.

The only thing I may change (other than adding a 2.5" Enforcer lift this week) is gearing. I'm curious how many of you with 37's have re-geared vs leaving the 4.10's. This issue isn't low end for me, it's more the lack of 8th gear on the freeway. Not a huge deal but something I'll definitely deal with at some point.

Click to expand...

Eddie has a great video in regards to the gearing. From everything I've seen (don't currently have a JL) it's a tradeoff. Yes you get 8th back, and yes you get more pep off the line, however, due to shorter gears, the downshifts fall into a taller gear, so your jeep will actually accelerate SLOWER (*at certain speeds) than a stock 4.10 one. I've seen a highway "race" between a 5.13 jeep and a 4.10 one on 37s, and the 4.10s will pull away. You have to decide WHERE you want the power to be. I am also completely disregarding the gas mileage penalty (*at certain speeds.)

* Also, this is very dependent on where you live. I live in the north east, so we don't have mountain passes and such, so 4.10s will be beneficial here. If I lived in Colorado, Nevada, Cali near sierras, etc, I would most definitely want more power (although if I lived there, I'd probably want the 2.0, as it will suffer altitute anemia a lot less.)

By the numbers, for best performance (closest to stock) you would be looking at a 4.59 gearing. Since that’s not true gear # and you’re moving more weight at this time, 4.88 would be reasonable.


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good to hear 37's on stock gearing does not bog the JL down like it did the JK

I've got a set of 37's I've been on the fence to put on before regearing but I think I'll buy a tuner and go for it :thumb: