Need some advice with regearing

[Ntegtmeyer]

Hey guys, I need some help here—thanks in advanced and sorry for the long post. Trying to give as much info as I can:
I recently installed the Mopar 2” lift and a set of 315/70/17 KO2’s. The ride and everything is just fine, however highway driving at 70mph and above isn’t very fun.

I have the 8 speed. Most of the time I sit in 6th, occasionally going into 7th. Very rarely do I go into 8th, everything has to be just right as others before have stated. So now I’m looking into regearing because I can’t live with it like that. I have a Sahara with the limited slip rear, so to my understanding I have the Dana 44 and the 30 up front? Anyways, I’ve been doing a ton of research and I can’t find exactly what I’m looking for based on my Jeep. I’ve seen a lot for the 2.0 or the manuals but nothing really for the 8 speed and 3.6

So based on what I’ve found, 4.10’s seem to be just fine according to rubicon owners and others says go for 4.56’s. I need your guy’s help to make up my mind because I want to do it right the first time. This is my DD and I do a lot of highway type speed, I go off-road about 1-2 times a month but don’t do anything crazy like rock crawling. Main things I’m looking for is getting my 7th and 8th gear back like normal, and better mpg. Cruising 65 I average around 16 mpg, 70 around 14.5-15mpg. I’d like to at least get 1-2mpg back and comfortably drive those speeds like before without feeling like my Jeep is being overworked.

So what’s the consensus? 4.10 or 4.56? I see Yukon sells 4.11 or 4.56 for my axles so I’m assuming the 4.11’s would be slightly better than the 4.10’s? Or am I looking at this wrong all together lol

Again sorry for the long post and I appreciate any help you guys can give me, I have completely no idea when it comes to this type of stuff. Thanks again, Nathan

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[Maverick909]

with the 8 speed i'd run the 35" tires with the 4.56 gearing. yukon is having pretty good deals at northrigid4x4 for the kits currently going on. i am planning to jsut switch my sport axle rear 44 with limited slip and the dana 30 up front on my sport to rubi take off axles with the 4.10 with my 6speed i do plan on going to 4.56 myself when i run 35 or 37" tires. not sure which yet though

 

[rustyshakelford]

4.88. 315s work out to around 35s.

Brett

 

[Maverick909]

4.88. 315s work out to around 35s.

Brett

yup 315=35" roughtly what would the rpm be at at 75 with the 6 speed. on 35's with 4.88

 

[limeade]

X2 on going to 4.88

 

[rustyshakelford]

yup 315=35" roughtly what would the rpm be at at 75 with the 6 speed. on 35's with 4.88

They all blur together. My 6 speed with 37s and 5.13s was around 2450-2500 rpm at 70. I’d venture a guess and say you’d be around 2200-2300 at 75

Brett

 

[Halstem1]

Trying to decide on gearing is the worst. Its fairly expensive for most and seems like everyone gets stuck between a couple options. I have no idea how you choose.

I have a 3.6 and 8 speed JLUR. Just for comparison, I have 4.10 gears and 37s. I would definitely say even with 35's you want to go lower than 4.10. 4.56 or 4.88 depending on how important highway mileage is. I think you'd be fine with 4.56 just comparing to mine. 4.88 would put you in the position I'm in with 5.13s, in that I don't want to be running super high RPMs on the interstate everyday.

A shop I talked to simply asked what speed I like to run on the interstate and go off that. So for me (37s), he said if I like to run 80-90 on the interstate, do 4.88. But if I like to run 70-80, go with the 5.13. That kind of makes sense to me because in town, the transmission will just make up the difference by up shifting. so I think it only matters when you get into 8th gear and how high you want the RPS. To be honest, I rarely run highway speed above 75. In Nebraska or eastern Colorado, I might set the cruise to 79. But for the most part, wind and sway and such, I like to stay around 70-75 because its more comfortable ride.

 

[limeade]

Something else to consider when deciding on which gear ratio to choose is what other mods have you added or are planning to add? In addition to larger tires (which are heavier than stock), bumpers, winch, sliders, armor, etc. all add weight. More weight equals less acceleration, lower MPG's, etc. Plus a lift adds more air resistance for your engine to overcome. If you're lifted and have or will add more weight, I would choose the lower gears (go with 4.88 vs 4.56). The lower gears will help with performance when you have added more weight vs a higher gear.

 

[Roky]

@Ntegtmeyer , IMHO..you should think about if you’re ever going to go up to 37s, and make that decision first. Re-gearing is an expense you only want to do once, lol.

 

[D60]

OP, 4.10 and 4.11 are identical for all practical purposes. It's entirely common for vehicles to have one up front and the other in the rear. They're so close it does not matter. At all

Some say manufacturers used to use one up front to make the front pull slightly more than the rear in 4wd, but I say that's an old wives tale. It had everything to do with BRANDS, ie a Ford 9" rear and Dana 44 front. Every manufacturer might have a ratio a TINY bit different for WHO KNOWS WHY reasons, but they're so tiny it's irrelevant

 

[Ntegtmeyer]

Thanks everyone for the reply, I’m not planning on going to 37’s as I think that’d be a bit much for an everyday driver. As far as the extra weight goes, I don’t plan on adding too much more. I already have the Mopar steel bumper in the front and the rugged ridge tire carrier on the back to hold my 35” spare. I don’t see myself adding an aftermarket rear bumper or changing it out unless it would be the Mopar steel one to match the front (I’m weird like that). So if I went with 4.56’s, would I see a gain in MPG and performance and I’d also get my 7th and 8th back on highway? I don’t know if I wanna go 4.88’s because I feel like my rpms would be pretty high

 

[Moto_21]

Ill sell you my d30 with 4.56 rcvs a torque locker and motobilt diff cover lol

 

[rustyshakelford]

Thanks everyone for the reply, I’m not planning on going to 37’s as I think that’d be a bit much for an everyday driver. As far as the extra weight goes, I don’t plan on adding too much more. I already have the Mopar steel bumper in the front and the rugged ridge tire carrier on the back to hold my 35” spare. I don’t see myself adding an aftermarket rear bumper or changing it out unless it would be the Mopar steel one to match the front (I’m weird like that). So if I went with 4.56’s, would I see a gain in MPG and performance and I’d also get my 7th and 8th back on highway? I don’t know if I wanna go 4.88’s because I feel like my rpms would be pretty high

I’d rather the rpm be a little higher than lower. These 3.6s don’t make much power and on the highway is where it really needs it. I want my engine working less and having more aggressive gearing helps that. I haven’t seen it in this thread but folks that think it’s ideal to have the hearing mirror stock when you add big, heavy tires aren’t looking at it the way we do. It requires more power to turn those bigger wheels, stock gears and tires are adequate. Lugging a modern gasser is worse than the higher rpms. Also, when on the highway if it doesn’t have the power to hold 8th, it’ll drop to 7th and to me the money spent to regear is now wasted.

Brett

To the shop that asked how fast you like to go on the highway, I like their thinking. That said, I never encourage or condone driving a lifted JL at 80-85 or higher so the gearing consideration is a non-issue with me. Just because you can do it, doesn’t mean you should rings in my head.

 

[Halstem1]

To the shop that asked how fast you like to go on the highway, I like their thinking. That said, I never encourage or condone driving a lifted JL at 80-85 or higher so the gearing consideration is a non-issue with me. Just because you can do it, doesn’t mean you should rings in my head.

Right? I'd never heard anyone ask that before and they were like the 5th shop I talked to. It makes sense though. For what its worth, I don't think he was condoning it, but his shop is in Nebraska and I think has customers that go north to the dakotas and west where the speed limits are higher. Like you, I just don't like driving above 75. But taking that logic into consideration, he has me leaning toward 5.13's on mine. I think at 70-75, my RPMs would be around 2400, maybe a little lower. That's what I'm hoping at least.

 

[Az-jewel]

I just dropped off my JLU Sport S manual, on 35’s, to be regeared today. Going to 4.88. Considered 5.13, but decided to stick with 4.88. IF I decided to get 37’s one day I’ll have to figure it out then, maybe a Rubi transfer case if I can find one.
I’m trussing my D30 front axle while in there too, and adding lockers! So excited to drive it! I’ve been nursing along my powerless rig for a while and can’t wait to have some oomph again!

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