What gear ratio should I install in my Jeep Wrangler TJ / LJ? (and other re-gearing FAQs)

[akajibio]

The 4.0 doesn't even start really making power until 2400 RPM, you don't ever want to be cruising at less than 2500 RPM and being over 3000 RPM at speed is no big deal. Having it be a manual transmission helps because you select what gears you want but with 4.88 you'd never want to be using 5th gear under 65 or 70 mph and 80 MPH would only be 3000 RPM.

Thank you so much for taking the time to explain your thoughts and I love the chart you have included. God bless you brother.

 

[NashvilleTJ]

Captain this jeep is my DD with a lot of highway/freeway driving. While I appreciate the value of deep gearing for off-road use, do you think 5.13 might be too deep for daily highway driving. Here in Las Vegas, 70mph is slow compared to the flow of traffic. Your thoughts? Remember, I have the 4.0 with 5spd manual.

The gearing recommendations we make here are not driven by offroad use, but rather the ratio recommendations are in fact driven by highway driving needs.

 

[JMT]

What he said ^^^

If you don't gear deep enough and your rpms in 5th are under 2650 and you're going 75mph and you come to even a slight incline, you will either start slowing down or have to downshift into 4th to keep speed. Then you are going 75mph and your rpm's are like 4000 or something. So, the better thing to do is gear it so you're running 3000+rpm's at 70mph. The numbers in this post are not meant to be exact. I'm just illustrating the principle of what happens. Looking at the chart for 5.13's I'd gear for 5.13's with your setup.

 

[jjvw]

Captain this jeep is my DD with a lot of highway/freeway driving. While I appreciate the value of deep gearing for off-road use, do you think 5.13 might be too deep for daily highway driving. Here in Las Vegas, 70mph is slow compared to the flow of traffic. Your thoughts? Remember, I have the 4.0 with 5spd manual.

Right back into the low effort lazyness you are famous for.

 

[mrblaine]

What he said ^^^

If you don't gear deep enough and your rpms in 5th are under 2650 and you're going 75mph and you come to even a slight incline, you will either start slowing down or have to downshift into 4th to keep speed. Then you are going 75mph and your rpm's are like 4000 or something. So, the better thing to do is gear it so you're running 3000+rpm's at 70mph. The numbers in this post are not meant to be exact. I'm just illustrating the principle of what happens. Looking at the chart for 5.13's I'd gear for 5.13's with your setup.

I was trying to help him figure that out before got so confused and offended. He'd rather be confused and offended.

 

[mrblaine]

Right back into the low effort lazyness you are famous for.

Shoe fits well?

 

[Mr. Bills]

Can you still see his posts? The best part of him blocking me is now I can actually call him names and he can't see it.

I think I've been blocked as well.


Edit:

Sure enough, when I log out and visit the forum, there he is.

I think I'll stay logged in.

.

 

[mrblaine]

I think I've been blocked as well.


Edit:

Sure enough, when I log out and visit the forum, there he is.

I think I'll stay logged in.

.

Sadly, I was really trying to help him figure this out.

 

[akajibio]

This is a very specific chart for guys wanting crawl ratios.

Horribly deep gearing for a daily driver.
The only thing accurate about the ratio recommendations is for guys running 35s or bigger or guys running the 4 angry squirrels. The smaller the engine or bigger the tire, the less room there is for compromise.

For the average guy 4.0L running 33s and the 32RE 3 speed automatic with no overdrive, 3.07s are perfect. 2200rpm at 70mph will return reasonable gas mileage and dropping to 2nd gear will give 3300rpm at 70mph, perfect for hills, headwinds and passing.

The only reason to go deeper is lift off the line. Far more important than power band at 70mph is getting started from a stop. With 3.07s off road, or on a forestry road, the range of speed in 4LO, in each gear makes for relaxed driving.... and the ability to do 60mph in 4LO. I'd go into 4LO as soon as I left the pavement with 3.07s. 90% of my wheelin' is mountain trails, forestry roads, old logging roads with the odd foray thru a ditch to reach a beach. I have zero need for ceawl ratios but I do want reasonable mpg.

Gear for the wheeling you do.

This is an old post, but I agree with you that some of us drive our jeeps daily. Not all of us use the jeep for crawling therefore some of these deep ratios will in fact wear you engine quickly, use more gas, and make your first gear useless. Your money, your choice, but the one size fits all mentality is not for most people. Take into account not only your engine size, transmission style, tire size, but also your intended use for the jeep. Most importantly, have fun.

 

[Chris]

Sadly, I was really trying to help him figure this out.

Some people do not want to learn, unfortunately.

 

[jjvw]

This is an old post, but I agree with you that some of us drive our jeeps daily. Not all of us use the jeep for crawling therefore some of these deep ratios will in fact wear you engine quickly, use more gas, and make your first gear useless. Your money, your choice, but the one size fits all mentality is not for most people. Take into account not only your engine size, transmission style, tire size, but also your intended use for the jeep. Most importantly, have fun.

Go right ahead and hitch your wagon to billiebob.

 

[machoheadgames]

This is an old post, but I agree with you that some of us drive our jeeps daily. Not all of us use the jeep for crawling therefore some of these deep ratios will in fact wear you engine quickly, use more gas, and make your first gear useless. Your money, your choice, but the one size fits all mentality is not for most people. Take into account not only your engine size, transmission style, tire size, but also your intended use for the jeep. Most importantly, have fun.

You repeatedly demonstrate that you don’t want to learn anything. Can you please provide some proof that lower gears wear the engine quickly? There is precisely zero evidence to support that, actually quite contrary, there is plenty of evidence to support that lower final drive ratios improve engine life because the engine achieves better oil pressure and less lugging when it’s kept at higher rpm and operating with greater mechanical advantage due to low ratios. But sure, listen to billiebob. With his logic you wouldn’t even be interested in regearing to begin with.

 

[akajibio]

You repeatedly demonstrate that you don’t want to learn anything. Can you please provide some proof that lower gears wear the engine quickly? There is precisely zero evidence to support that, actually quite contrary, there is plenty of evidence to support that lower final drive ratios improve engine life because the engine achieves better oil pressure and less lugging when it’s kept at higher rpm and operating with greater mechanical advantage due to low ratios. But sure, listen to billiebob. With his logic you wouldn’t even be interested in regearing to begin with.

Billiebob, can you show evidence that keeping your RPM high does not effect the wear of your engine? Sustained high RPM is better for the life of your engine? Ill wait for the evidence-based answers.

 

[machoheadgames]

Billiebob, can you show evidence that keeping your RPM high does not effect the wear of your engine? Sustained high RPM is better for the life of your engine? Ill wait for the evidence-based answers.

I am not billiebob. You quoted billiebob before.

You made the claim about engine life, you can be the one to back it up with evidence-based input.

 

[akajibio]

I am not billiebob. You quoted billiebob before.

You made the claim about engine life, you can be the one to back it up with evidence-based input.

You will keep following your own knowledge based beliefs no matter what anyone says. But in general our jeep motors where not designed to live in a higher RPM range due to stress, friction, heat, and bearing wear. I know that revving the engine intermittently or short burst of acceleration are good in that it burns off carbon deposits and can "clean out" deposits. But prolonged high RPM is an unnecessary stress on the engine unless it was a race car design. The jeep 4.0 is an old design that operates optimally in the 2-3K RPM range.

Automotive engineers generally agree that while occasional bursts of high RPM operation are acceptable and even beneficial for an engine's health (e.g., burning off carbon deposits), sustained high RPM driving in Jeeps (or any production vehicle) accelerates engine wear, generates excess heat, and can reduce the overall lifespan of engine components.

 

[machoheadgames]

You will keep following your own knowledge based beliefs no matter what anyone says. But in general our jeep motors where not designed to live in a higher RPM range due to stress, friction, heat, and bearing wear. I know that revving the engine intermittently or short burst of acceleration are good in that it burns off carbon deposits and can "clean out" deposits. But prolonged high RPM is an unnecessary stress on the engine unless it was a race car design. The jeep 4.0 is an old design that operates optimally in the 2-3K RPM range.

Automotive engineers generally agree that while occasional bursts of high RPM operation are acceptable and even beneficial for an engine's health (e.g., burning off carbon deposits), sustained high RPM driving in Jeeps (or any production vehicle) accelerates engine wear, generates excess heat, and can reduce the overall lifespan of engine components.

Dude, just stop. At this point you’ve already made up your mind and are just seeking confirmation bias to confirm the decision you already made. The response you posted was definitely generated by AI and states nothing useful. Chrysler already decided that over 3000 rpm was perfectly fine to cruise at because the factory 3 speed autos were regularly over 3200 rpm on the highway and they didn’t bat an eye at all - the engines last perfectly fine in those applications.

just regear your jeep already and quit seeking out opinions from only people who already agree with your stance.

 

[jjvw]

I am not billiebob. You quoted billiebob before.

You made the claim about engine life, you can be the one to back it up with evidence-based input.

@akajibio and billiebob should get married and have slow, under-performing children together.

 

[L J]

Sustained high RPM

What does the area marked by the yellow arrow indicate?

Ill wait for the evidence-based answers.

demands: evidence-based answers
provides: anecdotes

The jeep 4.0 is an old design that operates optimally in the 2-3K RPM range.

false

 

[Apparition]

What does the area marked by the yellow arrow indicate?
View attachment 656039

 

[mrblaine]

You repeatedly demonstrate that you don’t want to learn anything. Can you please provide some proof that lower gears wear the engine quickly? There is precisely zero evidence to support that, actually quite contrary, there is plenty of evidence to support that lower final drive ratios improve engine life because the engine achieves better oil pressure and less lugging when it’s kept at higher rpm and operating with greater mechanical advantage due to low ratios. But sure, listen to billiebob. With his logic you wouldn’t even be interested in regearing to begin with.

BB would have been more believeable if some of his stuff wasn't so far out there that no one could believe it. Some of that stuff about zipping his 3500 lb chimney sweep trailer up the mountains with ease on big tires are just not possible. But, if that is what Mr. Jibio wants to go with, by all means, have at it.