Gear Ratio / Gas Mileage - Jeep Wrangler Forum
Jeep Wrangler Forum

Go Back   Jeep Wrangler Forum > JK Jeep Wrangler Forum > JK General Discussion Forum

Join Wrangler Forum Today


Reply
 
Thread Tools

Please support our sponsors and let them know you heard about them on WranglerForum.com
Old 01-21-2011, 03:08 PM   #1
Jeeper
 
SBJeep's Avatar
 
Join Date: Jan 2011
Posts: 15
Gear Ratio / Gas Mileage

First post here.
This forum is great. Tons of helpful information and reviews.
First time Jeep owner. Purchased a 2007 Jeep Wrangler X about 6 months ago.
I'm running a 4" lift with 35's. After market drive shaft. No other engine or body mods.

Gas mileage is horrible. I've been tracking it and it seems to be around 11mpg.
I've been searching this site, and it seems that the only real difference makers in the gas gains game, is the Superchips Flashpaq and gears.
The previous owner installed the lift and tires. I'm not sure if he re-geared when he went tall and big. How do I find out which gears I'm running?
Second part to that question: if the gears are stock, what do you guys recommend or... have had the best luck with for my set-up I listed above.
Driving: Daily driver, reg road trips (300-500 miles), some trail driving (light). Not a lead foot. On freeway or highway, max speed is 70mph.

I want to get into more trail and off-roading (live in Cali so plenty of places to go and expand), but I don't think rock crawling will ever be the main focus. I need a set-up that gives me the best daily use with options for weekend fun.

Any other suggestions to get the gas mileage up to at least the mid-teens? Like I said, scouring through here, seems like nothing else really helps according to you guys.

I'd appreciate the input. I'd like to get the gears and gas down right to keep me away from the fill-up station so much...before I start adding other items from the wish list.

Thanks.

SBJeep is offline   Quote Quick Reply
Old 01-21-2011, 03:26 PM   #2
Jeeper
 
JeeperJake's Avatar
 
Join Date: Jul 2010
Posts: 2,908
Just rolled my first 1000 miles on a used 08 2 dr Sahara.

I was worried about mileage initially.

This is stock 18" factory tires, no lift, 3.73 gears, auto.
Last tank gave me 23.4 mpg on easy highway run, a little city. Haven't had it in any trail rides yet. Overall mileage seems 20+, I'll have to get my little notebook to post details.

I've heard the lift kits add considerable extra drag. There is a difference in my gearing/economy between 65 and 70. Haven't got a current link to the aerodynamic resistence/drag but there is a sharp break around that speed IIRC.

I'm finding best economy for me in the 1500 rpm range which is about 67 mph indicated.

Good luck.

__________________
get in--buckle up--hang on
"soothing agricultural implement/personal servant/Walter Mitty multidimensional access utility device conveniently travels on pavement when necessary and often keeps me warm/cool/dry/soothed as needed."
JeeperJake is offline   Quote Quick Reply
Old 01-21-2011, 03:27 PM   #3
MARGARET, 10-14-51\6-1-12

WF Supporting Member
 
GREEN-MACHINE's Avatar
 
Join Date: Aug 2010
Location: PEOPLES REPUBLIC OF MASSACHUSETTS
Posts: 10,260
first is it a stick or auto, stick i would go with 5.38 gears auto i would go with 4.88
the check the ratio you could pull the diff cover of and look on the ring gear it will be stamped there or jack up your jeep put a mark on the drive shaft and 1 on you tire rotate the tire and count how many times it turns for 1 spinn of the tire,
__________________

life is too short to be taken seriously all the time,,,, go buy a MR.potato head and have some fun.
GREEN-MACHINE is offline   Quote Quick Reply
Old 01-21-2011, 04:00 PM   #4
Jeeper
 
tuff2010's Avatar
 
Join Date: Dec 2010
Location: Weatherford TX
Posts: 355
I have a 2010 with a auto tranny, running a Trailmaster 3/5 lift and 35 inch dunlops with 5:13's and have been getting around 18mph, without the gears I was getting 11-13 depending on if the wind was blowing, LOL..
tuff2010 is offline   Quote Quick Reply
Old 01-21-2011, 05:22 PM   #5
MARGARET, 10-14-51\6-1-12

WF Supporting Member
 
GREEN-MACHINE's Avatar
 
Join Date: Aug 2010
Location: PEOPLES REPUBLIC OF MASSACHUSETTS
Posts: 10,260
Quote:
Originally Posted by tuff2010 View Post
I have a 2010 with a auto tranny, running a Trailmaster 3/5 lift and 35 inch dunlops with 5:13's and have been getting around 18mph, without the gears I was getting 11-13 depending on if the wind was blowing, LOL..
what rpm's you turning at 70mph.
__________________

life is too short to be taken seriously all the time,,,, go buy a MR.potato head and have some fun.
GREEN-MACHINE is offline   Quote Quick Reply
Old 01-21-2011, 06:16 PM   #6
Jeeper
 
JeeperJake's Avatar
 
Join Date: Jul 2010
Posts: 2,908
from Wikipedia:

POWER:
Power

The power required to overcome the aerodynamic drag is given by:

P_d = \mathbf{F}_d \cdot \mathbf{v} = \tfrac12 \rho v^3 A C_d

Note that the power needed to push an object through a fluid increases as the cube of the velocity. A car cruising on a highway at 50 mph (80 km/h) may require only 10 horsepower (7.5 kW) to overcome air drag, but that same car at 100 mph (160 km/h) requires 80 hp (60 kW). With a doubling of speed the drag (force) quadruples per the formula. Exerting four times the force over a fixed distance produces four times as much work. At twice the speed the work (resulting in displacement over a fixed distance) is done twice as fast. Since power is the rate of doing work, four times the work done in half the time requires eight times the power.

~~~~~~~~~~~~~~~~~~~~
In solving previous vehicle cooling issue on a pusher bus, I had to delve into the effects of the low pressure pocket formed at rear and under the rear mount engine, as related to the air flow into the cooling scoop on top of the bus. One would think moving thru the air on land was not so concerned with the mathematics of fluid dynamics and partial pressure waves regarding turbulence.

The brick-like Jeep shape moving squarely thru the increasingly more resistance air pressure is associated also with the increasing drag in the pocket behind the vehicle. Also there are under-vehicle effects serving to suck rolling efficiency.

The more naked hangy-down things and open spaces under the vehicle, the greater the increase in air resistance and more fuel it takes to go a given speed.

We tend to overcome this by pressing down harder on the skinny pedal. Going faster, independent even of gearing and rolling resistance of tires, requires more fuel, whatever engine is involved.

!~~~~~~~~~~~~~~~
sorry the formula didn't copy properly
__________________
get in--buckle up--hang on
"soothing agricultural implement/personal servant/Walter Mitty multidimensional access utility device conveniently travels on pavement when necessary and often keeps me warm/cool/dry/soothed as needed."
JeeperJake is offline   Quote Quick Reply
Old 01-21-2011, 10:12 PM   #7
Jeeper
 
tuff2010's Avatar
 
Join Date: Dec 2010
Location: Weatherford TX
Posts: 355
Quote:
Originally Posted by green-machine View Post
what rpm's you turning at 70mph.

2450.....
tuff2010 is offline   Quote Quick Reply
Old 01-22-2011, 12:05 AM   #8
Jeeper
 
joe002's Avatar
 
Join Date: Nov 2010
Location: Phoenix, AZ
Posts: 1,185
Quote:
Originally Posted by GREEN-MACHINE View Post
first is it a stick or auto, stick i would go with 5.38 gears auto i would go with 4.88...

Did you get that reversed? The manual turns higher RPM on the freeway than the Automatic. I have 5.38s in my automatic, and the theoretical RPM with 35's in OD is 2,495 but with my 35" KM2s I'm turning around 2,550. The theoretical RPM of you engine in a 6 speed at 70 MPH with 5.38s would be 3,038.

joe002 is offline   Quote Quick Reply
Old 02-16-2011, 07:20 PM   #9
Jeeper
 
SBJeep's Avatar
 
Join Date: Jan 2011
Posts: 15
It's an auto.

Running at 70mph, it runs about 3K in rpm.

I understand all the drag vs tires vs lift. I'm not swapping out anything to make it smaller. I've just noticed most on here talk about high teens for mileage with lifts and tires, so I'm trying to get to that point.

I thought I'd get more response on the gear ratio. Thus far I've got a 5.13 recommendation. And according to Joe's chart, 5.13 would put me right about in the middle.
SBJeep is offline   Quote Quick Reply
Old 02-16-2011, 09:00 PM   #10
Jeeper
 
ZOMB1E's Avatar
 
Join Date: Sep 2010
Location: Central Wisconsin
Posts: 483
I have a manual with 35's and 4.88 gears. On the highway I hover around 3k rpm. Gas mileage is approximately 13 mpg.

Sounds like your rig has been regeared already to me.
__________________

ZOMB1E is offline   Quote Quick Reply
Old 02-17-2011, 01:26 PM   #11
Jeeper
 
SBJeep's Avatar
 
Join Date: Jan 2011
Posts: 15
I missed a digit in my fast typing. At 70mph, it hovers at 2.3K RPM

SBJeep is offline   Quote Quick Reply
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the Jeep Wrangler Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Thread Tools

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Quick Question for Gear Ratio burton160w TJ Tech Forum 2 12-11-2010 07:34 PM
What gear ratio oIIIIIIo TJ Tech Forum 6 11-10-2010 09:09 AM
Gear Ratio Causing Problems? RoyalCask TJ Tech Forum 4 04-19-2010 09:25 AM
Which Gear Ratio Dan JK Tech Forum 7 07-22-2009 11:23 AM
axle gear ratio zpratt4 TJ Tech Forum 18 10-16-2008 02:12 AM



Download our Mobile App

» Network Links
»Jeep Parts
» Featured Product

All times are GMT -5. The time now is 11:46 AM.



Jeep®, Wrangler, Liberty, Wagoneer, Cherokee, and Grand Cherokee are copyrighted and trademarked to Chrysler Motors LLC.
Wranglerforum.com is not in any way associated with the Chrysler Motors LLC