thnks guys for your replies


Jpop

I don't know alot about regearing, but i think with 31s and 5.13 , there will be no speed at all onroad , right ?: , but i dunno how will be the driving at offroad

i got k&N CAI and gibson dual catback, throttle body spacer

and i got the sc flashqap , and m really happy with it , but i still want more power

so what do u guys recommend for me to do more, i need something with good performance and good price too :p ?

 

Where did this chart come from? It looks to be based on someone's opinion of what acceptable is to be honest, which is quite subjective. It shows stock Rubi + 32's to be just into the yellow zone. My personal experience was this was good. I'm currently running 35's with 4.10's and I find it to be a bit on the meh side, but certainly acceptable. I'll probably upgrade gears in the future but no way would I go over 5.13's on 35's, will probably just do 4.88's.

 

its not a car, either way re-gearing makes a difference with any tire size but look at some charts and you'll see that a regear will have higher rpm on the highway

 

Your RPMs will be too high at highways speeds with 31 inch tires and 5.13s. Wait until you go up to a taller tire to do a regear.

 

The chart is a direct result of the power curve of the 3.8L engine, the power needed to propel a JK at speed, including aero drag, gross weight, drivetrain loss, elevation and the grades in which the vehicle travels on. It is meant as a reference and was largely created to dispel the use of dated 1:1 transmission ratios and the very vast differences between automatic and manual transmissions, both now equipped with an overdrive gear.

Certainly it's subjective, but it was also created after reading hundreds of posts and the shared experiences of people who have and have not re-geared. Then it's backed by the physics and power requirements to make a JK go.

I'm more than willing to make edits and go into details of how the numbers were derived. I said that when I first posted the chart and to date no one has taken me up on it. I look at other charts and they aren't nearly as robust, and no others that I am aware of make provisions for OD and the difference in transmissions.

I'll also make note that the factory makes no differentiation of a Rubicon with an automatic transmission and manual despite the gear sets being more than 20% different.

 

What would you consider to be too high of rpms?

 

You have covered the things you can get out of the engine in terms of getting power out. The only other way to get more power out is to increase your rpms which is what a set of gears would bring you.

5.13s, 31s and 3,000 rpm gets you over 75mph. How much faster do you want to go?

 

Did you put it together? That is awesome! I can imagine this has been a ton of effort, I'll do a bit more in depth investigation as my experience based on my current setup and send that info to you for some hard numbers as opposed to a qualitative discussion....Just more data to add to your great chart.

 

I would totally regear to 5.13s if you have the cash and don't mind losing fuel mileage. I think it would drive great. It would have the power that they forgot to give it at the factory.

 

It actually wasn't all that much work. The chart took about 20 minutes, calculating hp needs to maintain speeds took a little longer, then so did putting together the scenarios as laid out. Just increased the grade and such. The interesting thing was that rotational weight of the larger tires is often overstated as well as what it really means to drive at altitude. The biggest thing is what it takes to drive a vehicle through air and space as it closely resembles a barn on wheels.