RPM’s with manual transmission

[KDB]

Like alot of us I’m patiently waiting for my 2 door build (MT 2 door rubicon) and only having familiarity with my ‘09 JK with the 3.8 I’m wondering about the cruising RPM’s for the 3.6.

My JK with MT I am right at 2000 RPM at 70 (3.21 gears) and wondering what to expect with the same set up (2 door MT) with my 3.6 pentastar with 4.10 gearing?

Basically I know the 3.8 liked to spin and does real well at higher RPM (mpg and torque) and wondering how the pentastar will compare. Does anyone know if there is a chart developed yet similar to the one for the JK (linked below)?

https://goo.gl/images/Cx0ceR

Sponsored

 

[DanW]

I don't have the exact numbers, but the 6th gear is extremely tall and will probably be similar to your 3.21 geared 6th gear at 70mph. The 5th gear is close to my JK Rubi 6th gear, both running 4.10's.

The Pentastar Upgrade in the JL gets over 90% of its torque from about 1200 rpms up. It is a nice, flat torque curve. Don't let the high torque peak fool you. It pulls strong from 1200 to redline. I'm running 35's and I feel it is strong, so with 33's it is even better.

My Pentastar outruns my buddy's 2 door 2012. Both are 6 speeds, and both have 35's on them. Mine slowly walks away. This engine is more powerful and the gearing in the 6 speed is better than the JK.

 

[KDB]

Thanks Dan for the comparison, this is helpful.

6th gear on my JK could only be used on flat highway stretches. Going through elevation in Colorado I would routinely be in 4th gear and barely able to stay at 60. Really looking forward to the new JL and hoping to at least get the same MPG that I’m getting on the JK.

My JK is averaging exactly 20 MPG over the last 120,000 miles per my Fuelly app and would be happy to get at least that with the JL

 

[DanW]

Thanks Dan for the comparison, this is helpful.

6th gear on my JK could only be used on flat highway stretches. Going through elevation in Colorado I would routinely be in 4th gear and barely able to stay at 60. Really looking forward to the new JL and hoping to at least get the same MPG that I’m getting on the JK.

My JK is averaging exactly 20 MPG over the last 120,000 miles per my Fuelly app and would be happy to get at least that with the JL

If you stay with the 33's on your Rubi, I'm betting you'll match that mileage. That will be great, because you'll have MUCH more off-road capability, and more power, both through the gearing and the upgraded engine. That adds up to a win/win for you! Can't wait to hear your report on it when you get it!

 

[KDB]

If you stay with the 33's on your Rubi, I'm betting you'll match that mileage. That will be great, because you'll have MUCH more off-road capability, and more power, both through the gearing and the upgraded engine. That adds up to a win/win for you! Can't wait to hear your report on it when you get it!

Thanks again, my buddy has had rubicon’s while I’ve been running my Sport S and whenever we go off road in AZ or UT I’m so jealous. After 9 years of my JK I’m ready to move up to the JL Rubi, still love my JK as she is my first Jeep and still debating if I should keep her or sell her.

 

[DanW]

Thanks again, my buddy has had rubicon’s while I’ve been running my Sport S and whenever we go off road in AZ or UT I’m so jealous. After 9 years of my JK I’m ready to move up to the JL Rubi, still love my JK as she is my first Jeep and still debating if I should keep her or sell her.

Same delemma! I just couldn't bring myself to sell the JK. It's staying put. My wife loves driving it, so she was 100% supportive.

 

[damage618]

So I just bought a 2018 Sahara JL 4dr 6sp manual. First off I went from a 2016 Silverado to this Jeep and I love it so far. the only thing that feels weird to me is the lack of power below 2000 rpms. Is it because I'm used to a 400hp v8? Seams like if i want to have power all the time I wont ever use 6th gear unless i'm going 70mph. dont get me wrong i drive around in what i think is too low of a gear most of the time and im still getting 21mpg city/hwy combined. anyone else have the same feeling as me, that it feels slugish 2000 rpms and lower?
P.S. I still have the factory 255/70/18 (32.06 inch tires) the reason im posting this is because im afriad to get bigger tires.

 

[Capricorn]

This is a matrix I made inputting the gear ratios for JL Rubicon with 4.10 diff ratio as attached.

 

[Capricorn]

So I just bought a 2018 Sahara JL 4dr 6sp manual. First off I went from a 2016 Silverado to this Jeep and I love it so far. the only thing that feels weird to me is the lack of power below 2000 rpms. Is it because I'm used to a 400hp v8? Seams like if i want to have power all the time I wont ever use 6th gear unless i'm going 70mph. dont get me wrong i drive around in what i think is too low of a gear most of the time and im still getting 21mpg city/hwy combined. anyone else have the same feeling as me, that it feels slugish 2000 rpms and lower?
P.S. I still have the factory 255/70/18 (32.06 inch tires) the reason im posting this is because im afriad to get bigger tires.

 

[Capricorn]

So I just bought a 2018 Sahara JL 4dr 6sp manual. First off I went from a 2016 Silverado to this Jeep and I love it so far. the only thing that feels weird to me is the lack of power below 2000 rpms. Is it because I'm used to a 400hp v8? Seams like if i want to have power all the time I wont ever use 6th gear unless i'm going 70mph. dont get me wrong i drive around in what i think is too low of a gear most of the time and im still getting 21mpg city/hwy combined. anyone else have the same feeling as me, that it feels slugish 2000 rpms and lower?
P.S. I still have the factory 255/70/18 (32.06 inch tires) the reason im posting this is because im afriad to get bigger tires.

Below 2000 rpm on the Pentastar engine would be lugging. From 2nd gear onward, shift at 2900-3000 rpm so you would be at at least 2300 rpm at the next higher gear, and that would be the minimum rpm from where you would accelerate.

 

[Litfuse]

Below 2000 rpm on the Pentastar engine would be lugging. From 2nd gear onward, shift at 2900-3000 rpm so you would be at at least 2300 rpm at the next higher gear, and that would be the minimum rpm from where you would accelerate.

You actually have to shift around 3500 rpms in 3rd gear and up or otherwise it falls below 2000 rpms.

To the OP, sixth gear will only be useful on flat highways when traveling over 70mph. I believe you are spinning just over 2000 rpms at 70mph in 6th gear.

 

[Badweissenbier]

And if you happen to be in wv you will find 6th gear worthless lol.

 

[rustyshakelford]

These threads are the push I need to regear to 5.13s when ours comes in. The 37s and 5.13 should put me around 2300 at 70. Hopefully it’ll help it out on the highway and starting off. Going to be running thru 1st quick though

Brett

 

[Biscuit]

FWIW, I made a round trip across the Appalachians from OH to VA last week and only had to drop to 5th on the longer grades to maintain speed. I think I dropped into 4th once or twice on a couple of steeper grades. Most of my time was spent in 6th at 65-70 mph (the speed limit) and averaged 24 mpg. This was in a bone stock JLUS. My rig turns 2000 rpm at about 73 mph in 6th and about 1800 rpm at 70.

 

[GoGators353]

I drove a rental JKU Sport manual last week and was amazed at how much better the clutch, engine, and MPG were over my JLU Sport. I know the Sport doesn't have the Rubi 4.10 so yours will be different but I was surprised how much I liked the JKU. The interior was lacking, no Sirius and no USB but the drive boring in the JKU but I was surprised about driving from Atlanta to Birmingham and not having to shift like I would in the JLU.

Sponsored