Trying to figure out if PO regeared - Jeep Wrangler Forum
Jeep Wrangler Forum

Go Back   Jeep Wrangler Forum > TJ Jeep Wrangler Forum > TJ Tech Forum

Join Wrangler Forum Today


Reply
 
Thread Tools

Please support our sponsors and let them know you heard about them on WranglerForum.com
Old 07-07-2014, 11:10 PM   #1
Jeeper
 
Phoenix TJ's Avatar
 
Join Date: Dec 2013
Location: Phoenix AZ
Posts: 20
Trying to figure out if PO regeared

Hi, so i have a 2000 Sierra, 4.0 5 speed. I am trying to figure out if the previous owner regeared it. It should have come with 3.73 new as the build sheet and tags on the diff's indicate
I have 31's on it that measure at 30".
By looking at the gear ratio calculator on grimjeeper.com which I have read that I can trust, something does not seem right.
At 2500 Rpm I am running exactly 75 mph
At 3000 rpm I am running exactly 90 mph
In 5th gear. Nv3500 tranny.

With 3.73 I should be going 85 mph at 2500 rpm and 102 mph at 3000 rpm according to the calculator. Can anyone confirm or dispute this?

With 4.11 gears I should be 77 mph at 2500 rpm and 92 mph at 3000 rpm according to this calculator, only 2 mph off of my actual speeds leading me to believe I have 4.11 gears.

My speedo tracks almost exactly with my gps as well as those radar activated speed limit signs that flash my speed at me as I drive by.

What do all of you experienced guys think of this?
Do you agree that the speeds at the given rpm indicate 4.11? Can anyone with similar tranny and tire size advise me if this sounds right?

I am getting ready to go to 33" tires and lockers , and looking into regearing. That is why I was looking at the charts and gear ratio calculators and noticed that something does not seem to add up. I am hoping to find that I already have 4.11 gears.

Would someone regear and leave the 3.73 tags on the diff's?

Thanks in advance for your help! This site is such a wealth of information and knowledge!

Phoenix TJ is offline   Quote Quick Reply
Old 07-07-2014, 11:49 PM   #2
Jeeper
 
hosejockey61's Avatar
 
Join Date: Oct 2012
Location: Aurora, CO
Posts: 1,186
A couple of options:

1. Open the diff and count the number of teeth on both ring and pinion and do the math.

2. Jack up the rear axle so the tires are off the ground. Mark your tire and your driveshaft so you can count the number of revolutions.

I have 4:56 gears. When my tire turns one full turn, the drive shaft spins ~4 1/2 times...so if you spin yours and it goes around ~3 3/4 times, then you have 3:73's....a little more than 4 turns then you have 4:11's.

hosejockey61 is offline   Quote Quick Reply
Old 07-08-2014, 12:06 AM   #3
Jeeper
 
Smitty4x4's Avatar
 
Join Date: Jul 2012
Posts: 337
I use the 2nd method he describes. I grease pencil and a jack is all you need. Takes about 5 minutes.
Smitty4x4 is offline   Quote Quick Reply
Old 07-08-2014, 07:14 PM   #4
Jeeper
 
Phoenix TJ's Avatar
 
Join Date: Dec 2013
Location: Phoenix AZ
Posts: 20
Thanks guys! I will get to it. Hoping for 4.11
Phoenix TJ is offline   Quote Quick Reply
Old 07-09-2014, 11:17 PM   #5
Jeeper
 
Smitty4x4's Avatar
 
Join Date: Jul 2012
Posts: 337
No problem. Let us know what you have.
Smitty4x4 is offline   Quote Quick Reply
Old 07-10-2014, 12:04 AM   #6
Jeeper
 
hosejockey61's Avatar
 
Join Date: Oct 2012
Location: Aurora, CO
Posts: 1,186
...and be sure to check both axles, not just one. You never know, somebody could have been on a budget and only regeared one axle with the intent of doing the other at a later date...
hosejockey61 is offline   Quote Quick Reply
Old 07-13-2014, 03:23 PM   #7
Jeeper
 
Phoenix TJ's Avatar
 
Join Date: Dec 2013
Location: Phoenix AZ
Posts: 20
Thanks to all for your help. I have confirmed 3.73 gears. Not to sure why their is such a large discrepancy in the speed vs rpm as compared to the gear calculators.
Phoenix TJ is offline   Quote Quick Reply
Old 07-13-2014, 03:43 PM   #8
Jeeper
 
Join Date: Apr 2013
Posts: 2,272
Realize it is driveshaft rotations to two full tire rotations with locked Diffy jack up both and one full rotation on both sides but with open Diffy jack up only one side and count for two full tire rotations on one side

If you jack up both with open other side rotates some and count is garbage
Digger84 is offline   Quote Quick Reply
Old 07-13-2014, 07:10 PM   #9
Jeeper
 
Phoenix TJ's Avatar
 
Join Date: Dec 2013
Location: Phoenix AZ
Posts: 20
Thanks! I did realize that I needed to go 2 full revs On the tire and had my kid hold my other tire. I have open differentials.
Phoenix TJ is offline   Quote Quick Reply
Old 07-13-2014, 07:45 PM   #10
Jeeper
 
Join Date: Jan 2014
Posts: 26
Dont use 5th gear to calculate. Comparing the transmission gear ratios for 5th are different, some list it as .73(grims), others have .78 ratio. Use 4th gear which has a 1:1 ratio

Using a few other sites that allows to manually input the numbers, Grimms 5th gear ratio likely is not listed correctly or not calculating properly. Even attempting to manually input the ratios on Grimms do not generate different results for 5th gear, be it .73 vs manually entered .78.

Hmm, well I think tis broke now. It stopped generating any numbers (closed browsers/cleared history/changed browser ).
Sarkaukar2000 is offline   Quote Quick Reply
Old 07-13-2014, 07:56 PM   #11
Jeeper
 
Join Date: Apr 2013
Posts: 2,272
Look at my post of today in thread

New guy with list of to-dos

Follow the directions and you will know ratio

The jeep is parked and transfer case in neutral and it matters not a wit what gear tranny is in

Digger84 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:
If you do not want to register, fill this field only and the name will be used as user name for your post.
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




» Network Links
»Jeep Parts
» Featured Product

All times are GMT -5. The time now is 12:32 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