37's on a Rubicon...

[MattT69]

Let's see. Rubicons come in 2dr (400 lbs lighter) or 4 door.

They come with manual 6-speed or automatic 8-speed (with short 1st geat, torque converter multiplication and great gear spread).

They come with engines varying from 260 ftlbs to 470 ftlbs.

They come with gearing between 3.73 and 4.88 (with 4.10s and 4.56 being more typical).

And 37x12.5 tires vary in weight from 65 lbs to 95 lbs.

Also, some drivers like to cruise on the highway at 55MPH while other are closer to 85MPH.

If you want a more helpful answer, you could include your choice of the above options.

I can tell you that on my heavy 4-door with 69lbs KO2 37x12.5 and my 2.0T engine and A8 with my preferred cruising speed of ˜75MPH, I feel no need to regear. 8th gear shows just fine at 75MPH and take off/offroad power is great. But that is my situation. What is yours?

You Nailed IT!!! The OP and some responders don't provide enough information about their build and engines choice to allow for relevant advice. All the variables that you mentioned need to be considered.

Most people in these forum falsely assume that all questions are based on the automatic 4-door wagon with the NA v6 engine...

There needs to be more information provided by the OP upfront as well as from the post-reply side so that others can look for the responses that best match their current or future build.

PS: I acknowledge that the more recent post have had more details and substance even though the original post was generic in nature. But maybe that's what drives up the reply side...

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[JLUCQ]

I have the 37" KO2 with a 2.5" Metalcloak lift and have felt no need to re-gear. The KO2 is smaller and lighter than every other 37 so my experience is going to be universal. I hit 8th regularly on the highway (although sometimes I wish it didn't hit 8th because it's such a slug and usually ends up downshifting pretty quickly). Mostly cruise at 70 and no issues. Doesn't feel much different than stock honestly. I've been running this setup for just over a year now.

 

[Hoote]

Let's see. Rubicons come in 2dr (400 lbs lighter) or 4 door.

They come with manual 6-speed or automatic 8-speed (with short 1st geat, torque converter multiplication and great gear spread).

They come with engines varying from 260 ftlbs to 470 ftlbs.

They come with gearing between 3.73 and 4.88 (with 4.10s and 4.56 being more typical).

And 37x12.5 tires vary in weight from 65 lbs to 95 lbs.

Also, some drivers like to cruise on the highway at 55MPH while other are closer to 85MPH.

If you want a more helpful answer, you could include your choice of the above options.

I can tell you that on my heavy 4-door with 69lbs KO2 37x12.5 and my 2.0T engine and A8 with my preferred cruising speed of ˜75MPH, I feel no need to regear. 8th gear shows just fine at 75MPH and take off/offroad power is great. But that is my situation. What is yours?

So what of someone has:
-a 4xe (375HP, 470lbs torque)
-4.10s
-37” tires at 73lbs (10lbs more than the 35s currently on it)
-mostly city driving at no more than 50mph
-off road trails 1x a month (moderate hills, deep snow)
-does a 250 mile road trip at 75mph once every2 months?

Would the extra HP and torque of the 4xe negate the need for a re-gear?

 

[gato]

So what of someone has:
-a 4xe (375HP, 470lbs torque)
-4.10s
-37” tires at 73lbs (10lbs more than the 35s currently on it)
-mostly city driving at no more than 50mph
-off road trails 1x a month (moderate hills, deep snow)
-does a 250 mile road trip at 75mph once every2 months?

Would the extra HP and torque of the 4xe negate the need for a re-gear?

No need to regear. You can drive it and you will see it performs totally fine.

You need to ask, what do you hope to achieve with a regear? With the 4xe low end torque, other than potentially gaining 0.1 or 0.2s in your 0-60MPH or slightly improving crawl ration, there is nothing a regear will do for you with the mission statement above.

 

[gato]

You Nailed IT!!! The OP and some responders don't provide enough information about their build and engines choice to allow for relevant advice. All the variables that you mentioned need to be considered.

Most people in these forum falsely assume that all questions are based on the automatic 4-door wagon with the NA v6 engine...

Exactly. The ZF-A8 and the high torque engines (2.0, Diesel, 392, 4xe) are "regear eliminators"

On the JL a regear should only be "recommended" (as in making a big difference) in very specific situations/combination.

Basically if you have a V6, manual, and heavy 35s or any 37s (specially on a 4 door) - strongly consider a regear depending on how you drive.

Everyone else with Autos (2.0, 4xe, Diesel, 392) only consider regearing for very heavy 37s or above.

Those with 3.6 Auto may desire a regear at one size/weight class lower than above.

But it is all about your set up, how you drive.

 

[JLJeepn]

JLUR 4Door 3.6L Auto
Metalcloak 3.5"
Nitto 38x12.50R17LT
Dana Spicer 4:88
Tazer Mini adjustments to Tires & Gears
(Full Build in Showcase)

HWY Flat drive here in pic.

 

[DavidArmen]

JLUR 4Door 3.6L Auto
Metalcloak 3.5"
Nitto 38x12.50R17LT
Dana Spicer 4:88
Tazer Mini adjustments to Tires & Gears
(Full Build in Showcase)

HWY Flat drive here in pic.

I was gna be like how on earth do you get ~15mpg avg with 38”s but then I saw the 4.88:1 regear. My 3.6auto JLUR gets ~15mpg on 35” ko2s on my stock 4.10:1. Although, It was about the same ~15mpg even on stock 33” ko2s so I didn’t see much of a drop.

 

[iddpaul]

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.

There are lot's of variables, but is it an "immediate need" - no, will your personal Jeep experience be better re-gearing - absolutely yes!

I'm driving a 2020 JLUR, 3.6, Auto, heavy 37"s (Ridge Grapplers), Bead Locks, 3.5 lift, tazer.

Started out with 35's and 4:10's, then moved to 37 Ridge Grapplers/Bead Locks and 4:10's for about 8 months. Drivable yes, but didn't see 8th much, on a trip couldn't hold 8th with any incline or a head wind, in fact even on a flat had to use "manual" to keep in 8th, mileage 15-17, sluggish getting going. Off road, just Ok. Obviously changing to 37"s will add more stress to the drivetrain and your wallet. IMHO this is a no-brainer driving the 3.6 JLUR, you will want to and certainly be happier re-gearing (I am). Start saving, and move to either 4:88's or 5:13's dependent upon your use/environment (do the math but also account for rolling mass, extra weight for aftermarket goodies and what/where you'll be going (highway, trail, rocks or a combo).

So was in some traffic, but IMO getting good MPG and shift points are excellent running 4:88's and 37's.

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