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Unread 03-10-2010, 05:25 PM   #1
TrueYJfan
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1989 YJ Wrangler 
 
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Transmission and T-case Help

I have an '89 YJ 4.2L with the factory BA10/5 trans. and I believe the NP231 t-case. I was wondering if anyone could tell me how to tell if it is the NP231 (I already looked for the tag but it is long gone) and also if I swap out the BA10/5 will the AX-15 bolt in or will I need a different t-case. Thanks

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Unread 03-10-2010, 05:44 PM   #2
markr1001
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ba10 has a 21 spline output and the ax15 has a 23 spline output, so you either need a input shaft or a whole new case...
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Unread 03-10-2010, 07:17 PM   #3
TrueYJfan
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Thanks, would I be able to take the input shaft out of the BA10 and put it in the AX15 or not?
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Unread 03-10-2010, 07:35 PM   #4
RikRotorhead
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Quote:
Originally Posted by TrueYJfan View Post
Thanks, would I be able to take the input shaft out of the BA10 and put it in the AX15 or not?
No. It's the output shaft of the transmission that is different.
In the t-case planetary gears there is an input gear that can be changed. It's $192 from advance adapters, plus shipping and tax.
It's best to get the NP231 with the AX15 trans. Everything will bolt up and you only need to change the pilot bearing on the flywheel, $7 at AutoZone.
The BA10/5 trans only had the NP207 and NP231/amc t-cases, both 21 spline. The AX15 uses the NP231/J, 23 spline.
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Unread 03-10-2010, 07:59 PM   #5
TrueYJfan
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Thanks how can you tell the difference between the NP231 amc and the 231j?
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Unread 03-10-2010, 08:10 PM   #6
monkeyhouse
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Quote:
Originally Posted by RikRotorhead View Post
No. It's the output shaft of the transmission that is different.
In the t-case planetary gears there is an input gear that can be changed. It's $192 from advance adapters, plus shipping and tax.
It's best to get the NP231 with the AX15 trans. Everything will bolt up and you only need to change the pilot bearing on the flywheel, $7 at AutoZone.
The BA10/5 trans only had the NP207 and NP231/amc t-cases, both 21 spline. The AX15 uses the NP231/J, 23 spline.
so if you get an ax-15 and the T/C the t/c will bolt up ok? That's cool.
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Unread 03-11-2010, 07:31 PM   #7
RikRotorhead
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Quote:
Originally Posted by TrueYJfan View Post
Thanks how can you tell the difference between the NP231 amc and the 231j?
There is a round tag on the back of the t-case that is red and silver that has the identification numbers on it.
If the tag is gone, look at the transmission. If the transmission has a seam running the length of it along the bottom, that is a BA10/5. The BA10/5 is a 21 spline whether it's a 231amc or a 207.
If there is no seam, it's an AX15 and it's a 23 spline which is the 231/J.

Quote:
Originally Posted by monkeyhouse View Post
so if you get an ax-15 and the T/C the t/c will bolt up ok? That's cool.
Yes. If you buy the tc with the trans (ax15) it will bolt up. BUT, the pilot bearing is a different size in the flywheel. You will have to pop that one out and put the one in for the AX15. They are available at any good auto parts store for under $10.
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