Need some advice with regearing

[rustyshakelford]

Quick question...is this little gear ratio adjustment specific just to manual transmissions?

Yes it’s for the manual only folks.

Brett

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[RidgeRider]

My 2020 Rubicon 4Cly 8sp stock did 19-22mpg. Put a bunch of stuff and 37s on it and now it is 15-16mpg but I still see 7th gear all the time, rarely 8th. The stock vehicle only showed 8th above 60mph and on fairly flat to downhill grades - this stayed the same with extra stuff and 35s but the 37s pretty much eliminated it. I still have plenty of performance, just low mileage. I looked at several threads and videos where re gearing helped performance (not my issue) but actually made mileage worse so I am holding off on any re gearing for now unless someone can refer me to some data showing that it materially improves mileage.

 

[mgroeger]

My 2020 Rubicon 4Cly 8sp stock did 19-22mpg. Put a bunch of stuff and 37s on it and now it is 15-16mpg but I still see 7th gear all the time, rarely 8th. The stock vehicle only showed 8th above 60mph and on fairly flat to downhill grades - this stayed the same with extra stuff and 35s but the 37s pretty much eliminated it. I still have plenty of performance, just low mileage. I looked at several threads and videos where re gearing helped performance (not my issue) but actually made mileage worse so I am holding off on any re gearing for now unless someone can refer me to some data showing that it materially improves mileage.

It won't improve mileage but you also need to think of mechanical advantage. Right now your transmission is having to do the work that a re-gear (proper gearing) is supposed to do. What does that mean long term for term for the transmission? I don't know. I'm of the mindset to keep things as close to how they were engineered to be used as possible and that would put me in the re-gear camp.
Also (3.6L, 8 spd on the Mrs. Jeep) she saw 8th gear all the time with the 4.10 gears in the Rubi axle. I'd be putting around town cruising at 45 mph and be in 8th gear. Now with 37s and still running 4.10s (haven't re-geared yet on this Jeep) I'll see 8th gear cruising at highway speeds if the conditions are right.

 

[Halstem1]

My 2020 Rubicon 4Cly 8sp stock did 19-22mpg. Put a bunch of stuff and 37s on it and now it is 15-16mpg but I still see 7th gear all the time, rarely 8th. The stock vehicle only showed 8th above 60mph and on fairly flat to downhill grades - this stayed the same with extra stuff and 35s but the 37s pretty much eliminated it. I still have plenty of performance, just low mileage. I looked at several threads and videos where re gearing helped performance (not my issue) but actually made mileage worse so I am holding off on any re gearing for now unless someone can refer me to some data showing that it materially improves mileage.

Brad at TrailRecon did a non-scientific video and showed a 1 MPG increase. That's what I would expect. Especially around town, the engine should be using less energy to get up to speed because of the increased torque. I'd echo @mgroeger on the rest. vehicle is going to be working more efficiently resulting in less wear. I haven't re-geared yet but I'm expecting significantly less shifting at highway speed. However, you've significantly increased weight and wind resistance with the modifications you've done. I wouldn't expect to see the same mileage you had before but might meet somewhere in the middle. If you only concern is MPGs, its unlikely you would recoup your costs directly related to fuel consumption. It would take 5-7 years to break even based on a 2-3 MPG gain based on average driving (15K miles per year).

 

[Az-jewel]

Just posting an update.
I have a 2018 JLUSport S, on mopar lift, 35” tites, 17” wheels, smittybilt front and rear bumper, 6-speed V6.
I just got 4.88 Yukon gears, trussed my front axle, and added arb air lockers. I took it off roading yesterday and am thrilled!! It crawled up and down rocks and hills like a champ!! No stalling, no gas pedal needed, no problem!!
I was at about 2500 rpm on the freeway at 75 in 6th gear!

I’m glad I chose 4.88! I think it’s perfect right now and will still work well if I go to 37’s. Plenty of power

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[ChattVol]

Just posting an update.
I have a 2018 JLUSport S, on mopar lift, 35” tites, 17” wheels, smittybilt front and rear bumper, 6-speed V6.
I just got 4.88 Yukon gears, trussed my front axle, and added arb air lockers. I took it off roading yesterday and am thrilled!! It crawled up and down rocks and hills like a champ!! No stalling, no gas pedal needed, no problem!!
I was at about 2500 rpm on the freeway at 75 in 6th gear!

I’m glad I chose 4.88! I think it’s perfect right now and will still work well if I go to 37’s. Plenty of power

View attachment 314839

View attachment 314843

Nice...how much did it cost for the truss, regear & ARB lockers?

 

[mgroeger]

Just posting an update.
I have a 2018 JLUSport S, on mopar lift, 35” tites, 17” wheels, smittybilt front and rear bumper, 6-speed V6.
I just got 4.88 Yukon gears, trussed my front axle, and added arb air lockers. I took it off roading yesterday and am thrilled!! It crawled up and down rocks and hills like a champ!! No stalling, no gas pedal needed, no problem!!
I was at about 2500 rpm on the freeway at 75 in 6th gear!

I’m glad I chose 4.88! I think it’s perfect right now and will still work well if I go to 37’s. Plenty of power

View attachment 314839

View attachment 314843

If you do move to 37s I'd HIGHLY recommend chromoly axle shafts. You've got lockers on there and IMO you will be rolling the dice with factory shafts and 37s.

 

[Az-jewel]

Nice...how much did it cost for the truss, regear & ARB lockers?

It was about $4500 out the door.

If you do move to 37s I'd HIGHLY recommend chromoly axle shafts. You've got lockers on there and IMO you will be rolling the dice with factory shafts and 37s.

I have considered those, thanks for suggestion! It’s on my list, along with brakes and steering if I do go to 37’s.

 

[Jank4AU]

So, I'm confused by a lot of this stuff. I have a 3.6L Sport S. I'm currently running 33" tires and added a Rubicon take-off suspension. There should be a warning that if you run anything larger than the stock street tires you'll lose 8th gear (just kidding, I know I'm responsible and I should have looked into it!). My question revolves around both regearing and swapping out axles. The Rubicon comes with 4.10 gearing and i have 3.45. If I regear, to 4.10 or 4.56 (so I can go up to 35's), what would be the effect if I were to later swap to a Rubi axle? Would just swapping axles be a better option? How robust are the Sport S axles? I'm a light off road weekend guy, will likely never do any really extreme off-roading.

I do eventually want a true lift kit and 35's. Should I just plan on regearing, swapping axles, axle swap and regear, or just buying a Rubicon down the road? LOL But I do love my current Jeep and what I've done to it.

Feedback and opinions are great appreciated.

 

[mgroeger]

So, I'm confused by a lot of this stuff. I have a 3.6L Sport S. I'm currently running 33" tires and added a Rubicon take-off suspension. There should be a warning that if you run anything larger than the stock street tires you'll lose 8th gear (just kidding, I know I'm responsible and I should have looked into it!). My question revolves around both regearing and swapping out axles. The Rubicon comes with 4.10 gearing and i have 3.45. If I regear, to 4.10 or 4.56 (so I can go up to 35's), what would be the effect if I were to later swap to a Rubi axle? Would just swapping axles be a better option? How robust are the Sport S axles? I'm a light off road weekend guy, will likely never do any really extreme off-roading.

I do eventually want a true lift kit and 35's. Should I just plan on regearing, swapping axles, axle swap and regear, or just buying a Rubicon down the road? LOL But I do love my current Jeep and what I've done to it.

Feedback and opinions are great appreciated.

Re-gear is going to run you $2k to have a shop do it. You can pick up a set of used D44s for around $3500 and swap them out yourself. Light off roading on the Sport axles and 33s you'd be fine. Dana/Spycer has commented that you can even Mall Crawl and LIGHT off road 35s on the Sport and Sahara axles. Going into more hardcore off roading and you would be wise to get some better legs under you.

 

[ChattVol]

So, I'm confused by a lot of this stuff. I have a 3.6L Sport S. I'm currently running 33" tires and added a Rubicon take-off suspension. There should be a warning that if you run anything larger than the stock street tires you'll lose 8th gear (just kidding, I know I'm responsible and I should have looked into it!). My question revolves around both regearing and swapping out axles. The Rubicon comes with 4.10 gearing and i have 3.45. If I regear, to 4.10 or 4.56 (so I can go up to 35's), what would be the effect if I were to later swap to a Rubi axle? Would just swapping axles be a better option? How robust are the Sport S axles? I'm a light off road weekend guy, will likely never do any really extreme off-roading.

I do eventually want a true lift kit and 35's. Should I just plan on regearing, swapping axles, axle swap and regear, or just buying a Rubicon down the road? LOL But I do love my current Jeep and what I've done to it.

Feedback and opinions are great appreciated.

Many places will do a regear for less than $2k. I was quoted $1600 by a shop in Chattanooga and the same at another outside Nashville. If you're running 33s/35s and will only do light offroading and mainly street use, there's no need to spend extra $ on rubi axles + labor. Keep your axles and regear to 4.56 if/when you go to 35s. I've talked with people with jk's running 37s on d30/d35 light offroading and mainly street use with no issues over a long period of time.

 

[Halstem1]

Feedback and opinions are great appreciated.

To me it would be a budget question. If you could find a deal on rubi axles and didn’t have to pay to ship, I’d go that way if I had the funds. I think the 4:10 is fine for 35s so it would be a 1 and done. Gears, 44s, lockers (I assume you can wire up factory lockers somewhere).

however, if budget doesn’t allow, see if you can do a gear swap for under 2k and see where that takes you. 3500-4000$ is a chunk of change, so I get that. Personally would be hard for me to convince my wife.

but I think the swap would be the most bang for your buck.

 

[Jank4AU]

To me it would be a budget question. If you could find a deal on rubi axles and didn’t have to pay to ship, I’d go that way if I had the funds. I think the 4:10 is fine for 35s so it would be a 1 and done. Gears, 44s, lockers (I assume you can wire up factory lockers somewhere).

however, if budget doesn’t allow, see if you can do a gear swap for under 2k and see where that takes you. 3500-4000$ is a chunk of change, so I get that. Personally would be hard for me to convince my wife.

but I think the swap would be the most bang for your buck.

So if you swap axles you don't have to also buy a ring and pinion regear kit?

 

[Halstem1]

So if you swap axles you don't have to also buy a ring and pinion regear kit?

I'm probably not the expert since I've never done it.... but I'm pretty sure not. they're already geared to 4.10. I've been driving on 37s and 4.10 gears for 15K miles. For the off-roading I do, I wouldn't re-gear if I hadn't bought a small travel trailer. Or wanted to "beef up" the axles down the road. So no, I don't think you need to pay for a re-gear. Pretty sure they bolt right up. The only thing I think you need to do is wire the factory e-lockers to something.... I think. There are some smart dudes on there that have done it, so I'll let them confirm.

 

[Halstem1]

I don't know why this never occurred to me before... I was playing with the gearing calculator putting in different sizes and ratios. I have a JLUR with 4.10 gears and 37s. I'm looking to go to 4.88 or 5.13, probably 5.13. I just realized that the overall ratio of my current 8th gear with 4.10 is the same as the overall ratio of 7th gear with 5.13. So if you have a rubi and aren't changing tires, you're new 8th gear will be the same as your current 7th gear on the interstate. Which is already where the jeep spends most of its time at highway speed.

Maybe this is common knowledge. It blew my mind. I drove 30 miles or so yesterday on the highway doing 79 mph in 7th. Its flat in Iowa so my jeep shifts into 8th more than others. But even if it gets into 8th, any acceleration or hill goes back to 7th. So really no difference other than way less shifting.

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