How to confirm gear ratio? - 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 09-26-2013, 01:01 PM   #1
Jeeper
 
Marthor's Avatar
 
Join Date: Sep 2013
Posts: 182
How to confirm gear ratio?

It's not on my invoice. I can find conflicting info online. How do I confirm which gear ratio I have??

2013 Wrangler Unlimited Sport S with automatic transmission. I found the transfer case ratio of 2.72

I looked all over on the tags on the bottom and couldn't find the gear ratio. It's either 3.21 or 3.73, but I want to know what I have.

I have the trailer tow group (not max tow). I have the anti-spin rear differential axle. Nothing tells me which ratio I have though.

Thanks for any help!

__________________
Marthor
2013 Wrangler Unlimited Sport, Black
Alpine Audio/Steps/Hard-Top/Tow Package/24S Option Package/Connectivity Group/Anti-spin Differential Axle
Marthor is offline   Quote Quick Reply
Old 09-26-2013, 01:06 PM   #2
Jeeper
 
Join Date: Nov 2012
Location: central pa mountains
Posts: 649
Jack the rear of the jeep up so the rear tires are off the ground. Turn the wheel one revolution. Count how many times the drive shaft turns. If it rotates 3.2 revolutions for one wheel turn, you have a 3.21, If it rotates 3.7 revolutions for one wheel turn you have a 3.73

__________________
I don't mind spending money, I mind wasting money
ztman is offline   Quote Quick Reply
Old 09-26-2013, 01:08 PM   #3
rotaredoM

WF Supporting Member
::WF Moderator::
 
panthermark's Avatar
 
Join Date: Aug 2011
Location: Chicago-land
Posts: 9,851
Images: 13
Log onto Jeep.com and enter your information....you can find out your build info on that site.
__________________
2013 Sahara Unlimited
Billet - Auto - 3.73 - Connectivity - Painted Hardtop - LSD - Remote Start - Saddle Leather - Side Airbags

I may mall crawl...but I look good doing it.....
panthermark is offline   Quote Quick Reply
Old 09-26-2013, 01:18 PM   #4
Jeeper
 
MotorCityJK's Avatar
 
Join Date: Jun 2010
Location: Sterling Heights, MI
Posts: 604
Should be a line item on the invoice or window sticker if you have the 3.73s. Max tow would have made them an automatic but the Trailer Tow can be had w/ either gear set.
__________________
2014 Anvil/Black JKUR - the Ellie-phant
auto/4.10s/max tow/730N/heated seats/connectivity/Prem soft top/remote start
Gone but not forgotten:
2010 Mango Tango JKUR - Big 'O/Molly
2008 Jeep Green JKUS
MotorCityJK is offline   Quote Quick Reply
Old 09-26-2013, 06:16 PM   #5
Jeeper
 
Marthor's Avatar
 
Join Date: Sep 2013
Posts: 182
I called Jeep and gave them my VIN and they told me my build is a 3.21 gear ratio.

So, is there any positive to 3.21? Better gas mileage perhaps?
__________________
Marthor
2013 Wrangler Unlimited Sport, Black
Alpine Audio/Steps/Hard-Top/Tow Package/24S Option Package/Connectivity Group/Anti-spin Differential Axle
Marthor is offline   Quote Quick Reply
Old 09-26-2013, 06:43 PM   #6
Jeeper
 
Plasticpirogue's Avatar
 
Join Date: Jul 2012
Posts: 521
NOTHING wrong with the 3.21s unless you plan to run big rubber in the future. By big rubber, I would say anything bigger than a 33" as you have 32"s from the factory.

In fact, if you talk to any good mechanical engineer, they will tell you that the lower sustained rpms (like cruising on the interstate) the better for long life.
Plasticpirogue is offline   Quote Quick Reply
Old 09-26-2013, 07:32 PM   #7
Jeeper
 
Marthor's Avatar
 
Join Date: Sep 2013
Posts: 182
Quote:
Originally Posted by Plasticpirogue View Post
NOTHING wrong with the 3.21s unless you plan to run big rubber in the future. By big rubber, I would say anything bigger than a 33" as you have 32"s from the factory.

In fact, if you talk to any good mechanical engineer, they will tell you that the lower sustained rpms (like cruising on the interstate) the better for long life.
Thanks for that!

For towing, I have a bicycle carry rack, a cargo rack, a motorcycle tow attachment and a ball for small trailers. I have zero need for the max tow package, so I think I'm better off with the 3.21 ratio gears for my needs. After thinking about it, I'm glad I have the 3.21 ratio.
__________________
Marthor
2013 Wrangler Unlimited Sport, Black
Alpine Audio/Steps/Hard-Top/Tow Package/24S Option Package/Connectivity Group/Anti-spin Differential Axle
Marthor is offline   Quote Quick Reply
Old 09-27-2013, 07:30 AM   #8
Jeeper
 
MotorCityJK's Avatar
 
Join Date: Jun 2010
Location: Sterling Heights, MI
Posts: 604
Quote:
Originally Posted by Plasticpirogue View Post

In fact, if you talk to any good mechanical engineer, they will tell you that the lower sustained rpms (like cruising on the interstate) the better for long life.
I would say this might be true if you don't try to regularly accelerate quickly or tow anything at all. Deeper gears make both of those MUCH easier on the engine and drivetrain and would far outway any increased wear from a small bump in rpm at a sustained rpm.

Personally I think the 3.21s are just Jeep's method of helping pull down the CAFE average but if using it more as a DD they work for a lot of people.
__________________
2014 Anvil/Black JKUR - the Ellie-phant
auto/4.10s/max tow/730N/heated seats/connectivity/Prem soft top/remote start
Gone but not forgotten:
2010 Mango Tango JKUR - Big 'O/Molly
2008 Jeep Green JKUS
MotorCityJK is offline   Quote Quick Reply
Old 09-27-2013, 09:38 AM   #9
rotaredoM

WF Supporting Member
::WF Moderator::
 
panthermark's Avatar
 
Join Date: Aug 2011
Location: Chicago-land
Posts: 9,851
Images: 13
3.55's would be great.
I debated between 3.21's and 3.73's. It all depends on where you live and how you use the Jeep. My only issue with 3.21's is that it limits the tow rating on the 4 door to 2000 pounds instead of 3500....outside of that, when I test drove both (back to back), I was fine with either.
__________________
2013 Sahara Unlimited
Billet - Auto - 3.73 - Connectivity - Painted Hardtop - LSD - Remote Start - Saddle Leather - Side Airbags

I may mall crawl...but I look good doing it.....
panthermark is offline   Quote Quick Reply
Old 09-27-2013, 11:47 AM   #10
Jeeper
 
derf's Avatar
 
Join Date: Oct 2012
Location: Cedar Rapids, IA
Posts: 1,352
3.55s would have been a perfect ratio for JKs with stock tires. Sadly, no one makes them.

I went with 3.21 gears because I knew I was going to do a lot of modification to my Jeep. No sense paying for 3.73 gears when you're going to swap in lockers and regear for 35" tires anyway.
__________________
2012 JK - 3.6/NSG370/NP241/D30/D44 - Grimm Jeeper
1986 J10 - 360/700R4/NP208/D44HD/D60FF - Truck Norris

My gear ratio calculator
derf is offline   Quote Quick Reply
Old 09-27-2013, 12:23 PM   #11
Jeeper
 
ohioviper's Avatar
 
Join Date: Sep 2012
Location: Chillicothe, Ohio
Posts: 1,802
For anyone staying with 33" and under tires 3:21 is a good ratio for mpg and yet it is still plenty zippy. Nothing wrong with it at all.
__________________

2013 JK mine
2000 TJ son's
ohioviper is offline   Quote Quick Reply
Old 09-27-2013, 06:54 PM   #12
Jeeper
 
MI JeepSkate's Avatar
 
Join Date: Feb 2013
Location: Dexter, MI
Posts: 266
mine came on the window sticker, said it like 12 times "3.73" this and 3.73 that. if its not marked, its probably a 3.21

__________________
Assistant manager at Discount Tire. Yukon 4.88's, Detroit locker rear, Ace C's, JCR daggar front, RK 2.5 MT, Fox 2.0's and an empty wallet
MI JeepSkate 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




Download our Mobile App

» Featured Product

All times are GMT -5. The time now is 12:34 PM.



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