Gearing question

[FireAnt21]

I am new to JEEP life. I recently upgraded my 2020 jeep wrangler 2.0t with 2 1/2 inch lift 35 inch tires pedal commander and paddle shifters. She is fun to drive. However, obviously, I’m not getting eighth gear on the highway. According to my bill sheet, I have 345 gears, M186 front and M220 rear. I am curious to what gear ratio I should go with again for now it’s fine, but my fuel economy is sucking a little bit. So I’m wondering what gear ratio would put me in a slightly better overall range should I go to 456 410 or 488. Please leave me the pros and cons of each and also a Brand choice of the gears as to avoid gear whine. Thank you.

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[grimmjeeper]

Depends on how and where you drive the Jeep.

Minimum for me would be 4.10. That's an acceptable ratio for 35s at low elevation and highway speeds.

4.56 is better if you spend a lot of time off road on the rocks and/or at higher elevation.

4.88 are good for rocks while still being useful on the highway. Though with 35s you'll be higher in the RPM band in 8th gear on the freeway. However not so much it's unreasonable.

With 4.88s you can upgrade to 37s later and still be in good shape. Though I would encourage you to beef up the front axle for 37s. More than you would for 35s.


The follow up question with the gear swap is what type of locker or limited slip you would like. If you put those in while you regear you're taking advantage of only doing and paying for the labor once. But the choice depends largely on how you plan to drive the Jeep.

 

[FireAnt21]

Depends on how and where you drive the Jeep.

The follow up question with the gear swap is what type of locker or limited slip you would like. If you put those in while you regear you're taking advantage of only doing and paying for the labor once. But the choice depends largely on how you plan to drive the Jeep.

I’m in Wisconsin and this is my daily. My build sheet says I have LSD. Mostly going to be a pavement princess. But who knows. I do want to hit some beginner trails.

 

[CarbonSteel]

Depends on how and where you drive the Jeep.

Minimum for me would be 4.10. That's an acceptable ratio for 35s at low elevation and highway speeds.

4.56 is better if you spend a lot of time off road on the rocks and/or at higher elevation.

4.88 are good for rocks while still being useful on the highway. Though with 35s you'll be higher in the RPM band in 8th gear on the freeway. However not so much it's unreasonable.

With 4.88s you can upgrade to 37s later and still be in good shape. Though I would encourage you to beef up the front axle for 37s. More than you would for 35s.


The follow up question with the gear swap is what type of locker or limited slip you would like. If you put those in while you regear you're taking advantage of only doing and paying for the labor once. But the choice depends largely on how you plan to drive the Jeep.

^^^^ 100% ^^^^

 

[entropy]

4.56s should be plenty for you given that you have the 2.0T.

Now let me ask you a question. Why does it bother you the transmission doesn't hit 8th gear? and, did you also re-programmed the computer for the 35s?

 

[FireAnt21]

4.56s should be plenty for you given that you have the 2.0T.

Now let me ask you a question. Why does it bother you the transmission doesn't hit 8th gear? and, did you also re-programmed the computer for the 35s?

Yes. Used my Tazer to do that. As close to 35 as I could. It doesn’t really bother me but I do highway driving quite a bit.

 

[entropy]

Yes. Used my Tazer to do that. As close to 35 as I could. It doesn’t really bother me but I do highway driving quite a bit.

- re-gearing for MPG?: Not guaranteed, I think most people report 1 to 2mpg extra. Very likely the MPG gained if any wont make up for the cost of re-gearing.
- re-gearing for better acceleration in 1st, 2nd gear (takeoff). Yeah this will improve if your jeep feels like a dog now.
- re-gearing for offroad use: You have a 4LO transfer case that does a lot more than going from 3.45s to 4.56s. Sure you'll get a bit better crawl speed and a bit more low end torque, but wont be a huge difference.
- re-gearing so that you see 8speed. Right now your transmission is finding the optimal ratio using the 7th gear, it will be the same once you re-gear but using 8th... essentially you would be going from a 7speed transmission to 8speed. This is a very small improvement that I am sure a lot of people wont truly notice.

So if the cost of re-gear, given benefits is still good enough for you go for it. I've never heard anyone said "I regret re-gearing". 3.45s is very high for 35inch tires. But keep in mind most people will always try to justify their expenses.

 

[azwjowner]

- re-gearing for MPG?: Not guaranteed, I think most people report 1 to 2mpg extra. Very likely the MPG gained if any wont make up for the cost of re-gearing.
- re-gearing for better acceleration in 1st, 2nd gear (takeoff). Yeah this will improve if your jeep feels like a dog now.
- re-gearing for offroad use: You have a 4LO transfer case that does a lot more than going from 3.45s to 4.56s. Sure you'll get a bit better crawl speed and a bit more low end torque, but wont be a huge difference.
- re-gearing so that you see 8speed. Right now your transmission is finding the optimal ratio using the 7th gear, it will be the same once you re-gear but using 8th... essentially you would be going from a 7speed transmission to 8speed. This is a very small improvement that I am sure a lot of people wont truly notice.

So if the cost of re-gear, given benefits is still good enough for you go for it. I've never heard anyone said "I regret re-gearing". 3.45s is very high for 35inch tires. But keep in mind most people will always try to justify their expenses.

You forgot one more reason -- regearing so you're not putting extra stress and torque on the output side of the transmission all the time.

 

[Steph1]

4.56 is absolutely perfect for 35s and the 3.6, so should also be perfect with the 2.0. I'm on 8th gear a soon as I hit 40mph and it's such a charm to drive compared to 3.45.

 

[grimmjeeper]

I’m in Wisconsin and this is my daily. My build sheet says I have LSD. Mostly going to be a pavement princess. But who knows. I do want to hit some beginner trails.

I'm personally not a fan of the factory limited slip. It's a clutch style that has durability issues.

If I was sticking with a limited slip I would spend the extra money on a helical gear limited slip like a TrueTrac or one similar to it.

A front limited slip is also useful, especially in the snow in Wisconsin. Though there are some things to look out for if you install one. The Front Axle Disconnect (FAD) system doesn't play well with a limited slip. You may or may not have it depending on your drivetrain configuration. Do you have the full time transfer case? It would be an optional extra. Otherwise you'd have the part time case.

 

[Steph1]

I'm personally not a fan of the factory limited slip. It's a clutch style that has durability issues.

If I was sticking with a limited slip I would spend the extra money on a helical gear limited slip like a TrueTrac or one similar to it.

A front limited slip is also useful, especially in the snow in Wisconsin. Though there are some things to look out for if you install one. The Front Axle Disconnect (FAD) system doesn't play well with a limited slip. You may or may not have it depending on your drivetrain configuration. Do you have the full time transfer case? It would be an optional extra. Otherwise you'd have the part time case.

I have to disgree, my family has had the factory trak-loc LSDs in XJs ,ZJs, TJs and now JL and none ever had a single problem.

 

[grimmjeeper]

I have to disgree, my family has had the factory LSDs in XJ, ZJ TJ and now JL and none ever had a single problem.

It got redesigned for the JK and JL. Lots of people have trouble, especially chucking teeth on the spider gears.

The older Jeeps were better. The clutch packs wear out but the diff stays intact a lot better than the new generation axles.

 

[entropy]

It got redesigned for the JK and JL. Lots of people have trouble, especially chucking teeth on the spider gears.

The older Jeeps were better. The clutch packs wear out but the diff stays intact a lot better than the new generation axles.

I mean my rear LSD is fine. But helical is always gonna be better than clutch type for a Jeep. And it is true that when it wears out it tends to eat the spider gears or damage the differential in other ways.

Here is a video on how to do the rebuild once you get the carrier out. And he also shows some of the damage inside the differential caused by the worn out LSD.

 

[grimmjeeper]

I mean my rear LSD is fine. But helical is always gonna be better than clutch type for a Jeep. And it is true that when it wears out it tends to eat the spider gears. I looked up a rebuild kit and the one I found even came with brand new spider gears lol. Cause by the time the LSD is out, you'll very likely also need to replace the spider gears.

It's worse with the JK and JL. The spider gears are prone to chipping and worse, even before the clutch plates wear out.

A lot of older LSDs don't break teeth even after the clutch packs wear out. I've seen axles with hundreds of thousands of miles on them with shot clutch packs but the bearings and spider gears are just fine.

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