NP231 23 spline to 21 spline -
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back > General Technical Discussions > Engines & Drivetrain > NP231 23 spline to 21 spline

Cyber Monday Sale Kick OffSavvy Aluminum Gas Tank SkidCyber Monday! 20% Off Jeep Tuners

Unread 03-01-2007, 10:10 PM   #1
Registered User
1997 TJ Wrangler 
Join Date: Oct 2005
Location: WV
Posts: 63
NP231 23 spline to 21 spline

Can the input shaft on the NP231 be easily changed from 23 spline to 21 spline.
The reason I ask is I found a good deal on a 231 with a tera low installed but it has the 23 spline input, I have the AX5 transmission in a 97 4 banger.


If you're not living on the edge you're taking up too much space
ROG97 is offline   Reply With Quote Quick reply to this message
Unread 03-26-2007, 03:07 PM   #2
Registered User
Join Date: Mar 2007
Location: Pismo Beach, California
Posts: 179

89 YJ Islander, White with blue pearl custom paint, 4.2 Nuttered, Holley carb, Light bar W/4 Kc daylighters, 32x11.50r15, Unknown lift, kenwood sound, Rockford fosgate Amp x2, Kicker Amp(1)
A work in progress...

2006 Ram 1500 TRX4 5.7 HEMI All stock
jeepdrvr101 is offline   Reply With Quote Quick reply to this message
Unread 03-26-2007, 06:13 PM   #3
H2 Recovery Team Member
sentinal02's Avatar
1992 YJ Wrangler 
Join Date: Feb 2003
Location: New York
Posts: 6,681
you're looking at a complete disassembly of both cases to swap it out. or just one if you want to spend the $$ and buy a new input gear. but yeah, it can be done.
RIP: '88 YJ 2.5L Ax-5 NP231
Posi-Loked. Herculined. Optima yellow top. 1" Shackle, 2" BDS. Cragar 397's Aussie front.

92 YJ 4.0L Ax-15 231
5" springs, 1" shackle 31's or 35's depending on my mood
sentinal02 is offline   Reply With Quote Quick reply to this message
Unread 03-26-2007, 11:40 PM   #4
Registered User
Join Date: Jan 2007
Location: edmonton , alberta
Posts: 5
I'm not 100 % on this .
but if the old t-case is the 2.72
and you want to go to 4:1 .the input shaft off the old case won't line up to the planetarys of the 4:1
laredo_man is offline   Reply With Quote Quick reply to this message

Quick Reply

Register Now

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

Email Address:


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

Suggested Threads

Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. is not in any way associated with Jeep or the Chrysler Corp.