Re-Gearing a JLU

[OBJLU]

Do you need new diff covers when regearing? I have the metal cloak skid for the rear.

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[intentsrig]

I don’t need to crawl at all do first will be useless. So instead of shifting st say 14 mph it’s more like half that?

shifting in 1st at 3,000 rpms is 12mph and at 2500 its 10mph

 

[LLRubylady]

shifting in 1st at 3,000 rpms is 12mph and at 2500 its 10mph

That’s not much different. And you have 5:14? Right now I shift at 14 mph just under 3000.
The off road shop suggested 4.88 for me. I don’t want to be overheated. Will never go above 35s.

 

[intentsrig]

That’s not much different. And you have 5:14? Right now I shift at 14 mph just under 3000.
The off road shop suggested 4.88 for me. I don’t want to be overheated. Will never go above 35s.

You don’t hve to worry about any overheating. I like 5.13’s even with 35’s. I’d say go 4.88 for a bit more mpg but 5.13 for better crawling on the rocks.

 

[Petey003]

Just installed 37s and ESS fault went away. Killed two birds with one mod...well that and the Rock Krawler 2.5 X-Factor lift.

IMO, 4.88 gears match PERFECTLY with 37s (measured 36" installed) on my 6-speed. Everything feels much smoother across the board. Still managed to pull off 17.2 mpg on a 22 mile trek into Phila today for work. Plenty of power in 4H.

Hey Man,

Love the rig. I’ve also got 37’s and 2.5” Rock Krawler X Factor (plus .5” Teraflex Load Level Spacers).

I’m considering doing 4.88’s due to tire size, front (+winch) and rear bumpers. I’m on the east coast and the mountains keep me stuck in 6th on the highway almost all the time.

Now that you’ve had your gears installed for a while what are you thoughts? What gear company did you use? Noise?

Thanks so much man!

 

[bgj1010]

Except, I can throw my factory wheels and tires back on the Jeep in 15 minutes if I need to go in for service. Can't do that with a ring and pinion swap.

I had my local dealership install my Mopar lift and 35s on my '18 JLU Sport S in order to make sure my warranty was not voided, and because they installed the lift purchased through them, the lift and all components are also now covered under the factory warranty. Adding a lift and tires should not void anything, but unless the dealer installs it they won't cover anything. Seeing we're in the gearing, axle, driveline thread, I also just got a quote from the dealership yesterday to install brand-new Rubi axle assemblies on my Sport S and wasn't too disgusted by the quote. All parts, labor and taxes rolled in will be $3950 front, $3350 rear. I'm totally going to do it, but need to wait until bonus time this December...

 

[bgj1010]

I obviously need to read up more on re-gearing, but as of now I have not felt or had any issues with my current setup with stock gearing in my JLU Sport S with a 2" Mopar lift and 35s. I did buy the Superchips Flashcal F5 and adjusted my tire size, as my shift points were pretty off until I did that, but otherwise it has plenty of balls in 1st all the way through 8th and I'm getting 20mpg average nowadays. It'll easily chirp the tires accelerating from a dead stop. I'm pretty confident that with the huge range of the 8spd auto that regearing isn't a necessity (with anything 35 and under), rather something you'd certainly want to do if you were on nasty trails 90% of the time or had 37s and up. For a daily that sees the trails every weekend, not sold on regear just yet. All that being said, before the new year, I plan on having Jeep dealership install new Rubicon axle assemblies, which are beefier than mine now (186/200 full-open) as well as lower stock gearing than mine. They quoted me $3950 front, $3350 rear, all parts, labor and taxes included. Everyone is gonna ask why not Dynatrac etc. Because I don't want that, and I don't want to spend that kind of outrageous money. It's a daily driver and bad enough I put it through the shit I do on our club runs. If it breaks, I'm fucked. If I need to have a beast exclusively for the trails, I'll buy a late model 2 door TJ or JK and make that the one I can afford to beat the shit out of and break/fix

 

[GoHack]

Anyone offering 3.73 gearing for the JL's?

I presently have the stock 3.45's, w/the Limited Slip Rear Differential in the rear, a 6 speed M/T, and riding on the stock 245/75R17 All-Terrain Tires, on my Sport JLU. If Jeep had offered a 3.73, I would of definitely bought it. They offered it as an option on the JK's.

The 3.73's are offered for the Gladiator I believe.

The power dies as soon as I hit any hills, where I have to downshift. On flat, level highways, I can keep it in 6th doing 70, but as soon as I start hitting any hills, no matter how slight, I have to downshift into 5th, and as they get bigger, into 4th.

4th seems to be the magic gear, which I tend to drive the most in.

From personal experience, having owned a few jeeps over the years, the 3.73 seems to be the best, for both highway and off-road, from my experience. The 4.10 on the Rubicon is too low, while the once offered standard 3.27 on the JK's, being way too high. The 3.73 seemed to be just the right gearing for both highway and off-road, even allowing for room for a larger 33-Inch LT285/70R17 tire from a Rubicon, w/o killing the torque that much.

 

[jaozus]

I plan on going from stock wheels to 31s, is regearing still necessary or only if im going to something crazy like 35s?

 

[UKCATS]

I plan on going from stock wheels to 31s, is regearing still necessary or only if im going to something crazy like 35s?

You should be fine.

 

[Petey003]

my 4.88 gears are in transit right now! Will be running Toyo 38s

Hey Matto!

I wanted to follow up from your thread here. I'm also going to 4.88's next week and wanted to get your feedback on them!

I have 2018 JLUR (auto) and have added 940lbs in armor and bumpers/gear (CAT scales weighed and verified). I'm looking for my 8th gear on the highway + some extra power. I'm in the North East and surrounded in mountains. The hills kill me lol.

I did some highway testing on a long drive. See below for results.

Really appreciate any insight on brand, installation, gear noise, and overall impression of the 4.88's.

Thank you so much!

 

[Ronbo Ranger]

Perhaps an example will provide clarity. I purchased a 2018 JLU Rubicon it came with 33" tires and has a 4.10 gear ratio. Suppose I would like to run 37" tires. The calculation to get back to factory specifications is 37 (the tire size I want to run) multiplied by 4.10 (the gear ratio currently in the vehicle) = 151.7 divided by 33 (the diameter of tires the factory provided) = 4.5969697 Now compare the results of our formula to the available gear sets and choose the gear set that most closely matches, in our case it would be 4.56

I'm currently running stock 33" BFGs @ 4.10 ratio/ So for 35" tires using this formula Gear ratio needs to be 4.34 ? IS it even worth it ?

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