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Old 10-03-2012, 06:37 PM   #1
Hogwrangler89's Avatar
Join Date: Sep 2012
Location: South central florida
Posts: 6

Is every np231 the same? Other than there's a 21 and 23 spline. Is there any electrical upgrades on the new ones? I have a 90 and the transfer case broke. The guy I'm buying one from says his has a plug on it and I don't think mine does?

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Old 10-03-2012, 07:10 PM   #2
Scooby88's Avatar
Join Date: Jan 2012
Location: Mid Michigan
Posts: 364
Yes I just ran into that issue,

They are both stamped 231J the one on the right is a 21 spline and the one on the left is a 23 spline.

To be continued....

You Don't Buy a Jeep, You Build One.

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Old 10-03-2012, 11:41 PM   #3

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Join Date: Apr 2012
Location: North Las Vegas
Posts: 9,483
The newer one have a speed sensor instead of cable driven speedo is hwat i hear. But if you have an SYE no issue or you could just swap the tailcones. Yes 21 and 23 spline difference between the AX4/5 and AX15 trans 4 bangers and 6 bangers.
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Old 10-04-2012, 07:09 AM   #4
roadyrob's Avatar
Join Date: Apr 2012
Location: west palm fla
Posts: 987
you can just swap your mechanical speedo drive to the newer case. like posted 4 cyl cases have 21 spline , 6 cyl are 23. there was a gear change in the newer cases (94 and up) but thats internal.
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