6-Speed JLUR with 35s vs 37s (no re-gear)

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I know a lot of people say you must re-gear when going to 37s with a 6-speed manual... But —

Has anyone driven a 6-speed JLUR on 35s and 37s and can describe the difference?

How huge of a difference are we talking in terms of power/acceleration?

Are you really in 3rd gear on the highway at high speeds?

Can you use 1st gear in 4-low without stalling?
  • Factory ordered a new 2021 JLUR and like many before me, I’m debating between 35s and 37s.
  • I’m not doing extreme rock crawling (yet?), maybe some minor tech stuff, but mostly mud and forest roads.
  • This is my daily driver, including highway and long trips for vacation with the family (to beach, other cities, camping, visit family, etc.).
  • Planning a 2” Mopar Lift, 17x9 wheels, 35s or 37s - All Dealer Installed
  • Buying 8yr Mopar warranty + Lift warranty, dealer said they will honor the warranty with 37s and there’s not a big diff between 35s and 37s (their words)
  • This post is not about warranty





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rustyshakelford

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35s have more drivability than 37s. 37s and 6 speed even with the rubicon 4.10s isnt optimal at all. Be prepared to stall it a bunch or slip it at every start until you learn it well. You’ll be in 5th on the highway. Maybe get into 6th but it won’t hold it if you encounter much of a grade. I couldn’t stand driving or wheeling mine on stock gearing so we regeared it pretty soon.

There will be posts saying it drives fine but as with anything, it’s people’s perception. What i didn’t like is perfectly acceptable to someone else.

brett
 
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35s have more drivability than 37s. 37s and 6 speed even with the rubicon 4.10s isnt optimal at all. Be prepared to stall it a bunch or slip it at every start until you learn it well. You’ll be in 5th on the highway. Maybe get into 6th but it won’t hold it if you encounter much of a grade. I couldn’t stand driving or wheeling mine on stock gearing so we regeared it pretty soon.

There will be posts saying it drives fine but as with anything, it’s people’s perception. What i didn’t like is perfectly acceptable to someone else.

brett
Thanks for the feedback. So you drove a 6-speed JLUR with 35s and 37s?

If so, the additional 1” in height and added weight impacted the ride by a lot?
 

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Thanks for the feedback. So you drove a 6-speed JLUR with 35s and 37s?

If so, the additional 1” in height and added weight impacted the ride by a lot?
Yes I've driven both.

My personal JL was a 6 speed on 37s. I would stick to 35s if you don’t want to regear or get the auto. I went 6 speed because I didn’t love the JK auto and the 8 speed was relatively new and unproven the the JL. I’m a believer now and have the 8 speed now. To me with stock gearing and 37s it wasn’t fun to drive.

brett
 
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Okay thanks, and with the 35s it was still fun to drive?

I don’t plan to re-gear because that would 100% eliminate my Mopar warranty on almost everything.
 

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Hey! So, I’m a perfect test case for you. Because I’ve done something “stupid”, and I’m happy to have done so.

I have a Willys with 38 Milestar Patagonia’s. So, 38’s on 3:45 gearing with a 6-speed.

I have zero issues with stalling, in any gear, 2H, 4H, or 4L.

I do only have a 4-speed transmission now, with an occasional overdrive in 5th if it’s flat or if I’m cruising at 80, and a very very rare 2nd overdrive of 6th if I’m on a long decline.

In 4th-

70mph is about 2100rpm
75mph is around 2250
80mph is around 2400

In 5th-

70mph is about 1700
75mph is around 1850
80mph is around 2000

The Jeep can’t accelerate anyways below 2k if you’re flat or going uphill, so normal cruising at 70 I’m happy to leave it in 4th. I still get 18-19mpg highway. I do have to downshift to 3rd or even 2nd for steep climbs. I’ve never had an issue holding up traffic.

Do I want to regear? Hell yes. Probably to 5:13’s. Am I going to wait until I blow the front axle and just go with Rubicon swaps? Yeah probably. No sense in wasting the sport axles.

Rubicon gearing, in 5th you’ll be around 68mph at 2000rpm, so you’ll spend your time in 5th and rarely in 6th.
 

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i have been runnin 35" KO2's for 41,000 miles. Never had any problem at on road, off road. City driving was kind of like a 3 speed. on trips to moab and back home to moab to home (2100 miles) I averaged 19.1 mpg each time. I wouldn't have re geared if I stayed with 35's. I recently made the decision to do 4:88's and 37" tires. This is absolutely perfect for me. I will be making a Colorado trip next month and will see how it does. I'm already hyper impressed.
You get to decide tho!
 

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37s on 4.10 rubicon gears here. It’s drivable. I’d like to regear whenever I can sneak the charge past my wife, but it is ok with stock 4.10s. May have to make a decision on stalling vs slipping the clutch when on steep inclines. I’ve stalled a few times. In 4lo I’ve never felt that 1st gear wasn’t low enough. But, I haven’t done extreme rock crawling. On highway, gas mileage is going to suck if you want to go fast, but I’m getting around 17 highway in 4th going 65-70ish. I actually have found my mpgs are worse in 5th gear on cruise control.
 

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Okay thanks, and with the 35s it was still fun to drive?

I don’t plan to re-gear because that would 100% eliminate my Mopar warranty on almost everything.
35s is fine, not great, but not bad. I would say tolerable. A lot of dealers can regear for warranty. They are usually the biggest hypocrites on this but if you’re lining their pockets, they can look past a lot of mods if there is a warranty claim down the road.

brett
 

mskillen

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I have a JLUR with 35s and I dont really have any complaints about it.
It basically went from a six speed to a five speed , 6th is pretty much not usable unless your going 75 plus mph.
I use 5th for long trips and that puts me about 2400rpm at 70 which is perfect for the engine.
I get about 18/19 mpg on the highway, offroad in 4Lo the jeep is still impressive.
I can crawl rocks and trails in 1st gear without stalling its very usable.
I do still plan to regear and have made an appointment for 4.88 gears.
I plan on going to 37s eventually, but currently with 35s and beadlocks wheels and tires are about 120lbs a piece, so you do notice the extra weight.
4.88s will give me back 6th gear and make the weight less noticeable, and it will put me about 2400 rpms at 70 in 6th gear with 35s and about 2200 rpms with 37s.
So the jeep is still fine with 4.10s and 35s, 37s might make it feel like a dog on the road and you might end up just using 4th as your final gear unless you regear.
 
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37s on 4.10 rubicon gears here. It’s drivable. I’d like to regear whenever I can sneak the charge past my wife, but it is ok with stock 4.10s. May have to make a decision on stalling vs slipping the clutch when on steep inclines. I’ve stalled a few times. In 4lo I’ve never felt that 1st gear wasn’t low enough. But, I haven’t done extreme rock crawling. On highway, gas mileage is going to suck if you want to go fast, but I’m getting around 17 highway in 4th going 65-70ish. I actually have found my mpgs are worse in 5th gear on cruise control.
How is acceleration when merging when you need to get up to speed on the highway or passing compared to stock (assuming you drove stock before)?

My biggest concern is loss of power and I’m trying to understand how much of a loss am I going to experience when compared to stock or even better, when compared to 35s.

I’m expecting less power/acceleration due to added weight. I’m not looking for a race car either. Where I live people drive aggressively and I need to be able to keep up in some scenarios (i.e. merging onto the highway). Will it be like driving a slow pinto?

Thanks again!
 

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How is acceleration when merging when you need to get up to speed on the highway or passing compared to stock (assuming you drove stock before)?

My biggest concern is loss of power and I’m trying to understand how much of a loss am I going to experience when compared to stock or even better, when compared to 35s.

I’m expecting less power/acceleration due to added weight. I’m not looking for a race car either. Where I live people drive aggressively and I need to be able to keep up in some scenarios (i.e. merging onto the highway). Will it be like driving a slow pinto?

Thanks again!
you can still keep it in the power, you just loose the benefits of a 6 speed and the spacing on the gears gets stretched out a little more.

brett
 
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you can still keep it in the power, you just loose the benefits of a 6 speed and the spacing on the gears gets stretched out a little more.

brett
So the cost of going to 37s is loss of 6th gear and it becomes more of a 4-speed.

So is the only reason going to 35s vs.37s because you want to use 5th gear more often?

Thanks again!
 

mskillen

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Going to 35s makes 6th inefficient for any on road gas mileage or performance.
37s will most likely take 5th and do the same thing.
So you would end up with a 4 speed, the rpms on the engine are important.
So ideally you want to keep your rpms in the 2200 to 2400 range with your final gear.
Just basing it on highway speed of 70mph.
That is the point where you will still make power and get your better gas milage.
The reason to regear would bring you closer to stock, even with the bigger tires, and to get your OD gears back.
If you do 35s you will be happy, if you do 37s you will be happy.
But your going to want gears eventually.
 

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