Axle Ratio vs. Top Gear Ratio - 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 10-20-2013, 09:21 AM   #1
Jeeper
 
WaltA's Avatar
 
Join Date: Sep 2013
Location: 3rd Planet, Sol system
Posts: 3,437
Question Axle Ratio vs. Top Gear Ratio

I have been reading various comments made in several threads, both here and at other sites, and I have a question.

Does the factory change the top gear ratio of the transmissions, to compensate for the axle ratio, such that you always end up with the same engine RPM at, say, 60 mph regardless if you have a 3.21, 3.73 or 4.10 rear end? If true, I would assume to attempt to maintain the same highway mpg rating.

Does anyone know?

__________________
Current Jeep:
2014 Wrangler Unlimited Rubicon X
Previous Jeeps:
1987 Wrangler Laredo
1999 Cherokee Limited (Up Country,Trailer Tow)
[All custom ordered, purchased new]
WaltA is offline   Quote
Old 10-20-2013, 11:14 AM   #2
Jeeper
 
MarineHawk's Avatar
 
Join Date: Dec 2011
Location: Virginia
Posts: 700
Nope. 5th gear auto in the 2012+ JKs is 0.83:1. 4th (the highest gear on pre-2012 models) is 0.69:1. That doesn't change depending on your diff gearing.

MarineHawk is offline   Quote
Old 10-20-2013, 12:58 PM   #3
Jeeper
 
gecko4's Avatar
 
Join Date: Aug 2013
Location: ontario
Posts: 892
Yup, Marinehawk is right,the lower the rear end gearing, the higher the engine will rev at a given rpm. The effect on fuel economy may be only modest though. It would be interesting if the fuel economy was rated for the different axle ratios.
gecko4 is offline   Quote
Old 10-20-2013, 02:41 PM   #4
Jeeper
 
WaltA's Avatar
 
Join Date: Sep 2013
Location: 3rd Planet, Sol system
Posts: 3,437
Thanks for the replies.

I had a hunch it was that way. I guess those others either were mistaken at what exact rpm their engines ran at 60 mph, or mistaken at what their axle ratio was.
__________________
Current Jeep:
2014 Wrangler Unlimited Rubicon X
Previous Jeeps:
1987 Wrangler Laredo
1999 Cherokee Limited (Up Country,Trailer Tow)
[All custom ordered, purchased new]
WaltA is offline   Quote
Old 10-20-2013, 03:46 PM   #5
Jeeper
 
MarineHawk's Avatar
 
Join Date: Dec 2011
Location: Virginia
Posts: 700
In case it's relevant, tire diameter will affect the RPMs at a given mph.
MarineHawk is offline   Quote
Reply

Thread Tools

Posting Rules
You may not post new threads
You may not 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




Download our Mobile App

» Featured Product

All times are GMT -5. The time now is 10:35 AM.


User Alert System provided by Advanced User Tagging v3.1.0 (Pro) - vBulletin Mods & Addons Copyright © 2015 DragonByte Technologies Ltd.

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