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Unread 06-18-2014, 05:26 PM   #1
T800
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T18 swap - info needed

Long story short: I need a 21 spline input gear for the NP231 that has a stickout of 2.12" and can't seem to find one.

The rest: I'm replacing the BA10/5 before it blows up on me with a Ford T18. Got a good deal on an AA 50-7501 21 spline t-case adapter which is supposed to fit 231 t-cases from the AX4, AX5, AW4, so I went with that. Novak shows all 21 spline input gears to be the short length so I thought I was in business. Apparently not. The BA10/5 input gear has a stickout of 1.2" and AA says 2.12" for this adapter.

While installing the SYE I found the transfer case was not in good shape and needed a rebuild. If I knew I'd have to change it anyway I'd have gone 23 spline ... this is how my luck goes.

I have been in contact with AA via email but they haven't provided any help as of yet.

Anyway, if anyone knows what the correct input gear would be and possibly where I could find one I would greatly appreciate it. The T18 is in and just waiting for a t-case.

Thanks

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Unread 06-20-2014, 09:35 AM   #2
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After more research, it would seem the NP231 behind the AX5 should have the long 21 spline input gear up thru 1996. Can anyone confirm that?

Problem is every place that sells NP231 input gears has no specs at all for them, including the Crown and Omix websites. What little is available is also inconsistent from site to site.

RockAuto lists the Omix-Ada 18676.08 for a 2.5L YJ, but of course they don't specify a transmission. They also list the same part for the 4.2L. Both can't be correct as one should be an AX5 and one a BA10.

The alternate part number for the above is 53006083, which is a Crown 21 spine, length unknown and said to fit 91-95 - doesn't that overlap the change in gear cuts

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Unread 06-20-2014, 10:29 AM   #3
axxxgijoexxxa
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Novak sells the input gears, I bought one from them. I found like you it's hard know exactly what you're getting from other sources.

Joe

Edit: Sorry just looked at novak's site looks like they only have 23 spline long.
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Unread 06-20-2014, 12:37 PM   #4
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Wierd AA calls for a 21 long. According to novaks info nothing ever came with a 21 long from the factory.

Joe
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Unread 06-20-2014, 01:09 PM   #5
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Agreed, that's why I thought I'd be ok with the input gear I had.

This article at Quadratec contradicts Novak's ...
http://www.quadratec.com/jeep_knowle...article-42.htm

I'm surprised AA can't or won't give me advice on which gear would work.

I'm starting to think the long 21 spline is either a myth or the Holy Grail of Jeep parts.

Thanks, Joe.
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Unread 06-20-2014, 03:14 PM   #6
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Seems to me when I emailed AA about an adapter they were fairly slow to respond. Good luck!

Joe
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Unread 06-20-2014, 04:15 PM   #7
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East Coast Jeeps tried to help. Said the Omix 18676.08 looked right but they couldn't guarantee it'd work for the application. I ordered one and will just return it if it isn't. I suspect it'll be a short.

Also going to hit the salvage yards in the AM and see what I can come up with.
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Unread 06-20-2014, 04:57 PM   #8
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I've got an AX-5, that was in an '88, sitting in my storage shed that I can measure stuff off of.

you just need how far the input gear sticks out from the front of the case?
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Unread 06-20-2014, 08:35 PM   #9
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Quote:
Originally Posted by crackedcornish View Post
I've got an AX-5, that was in an '88, sitting in my storage shed that I can measure stuff off of.

you just need how far the input gear sticks out from the front of the case?
Awesome. Yes, the stickout from the mounting surface to the end of the gear.


Thanks very much.
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Unread 06-21-2014, 06:18 AM   #10
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OK, just did some measuring for ya'...from the mounting surface to the end of the input gear = 1.15"


I'm afraid to say the early gear isn't what you need
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Unread 06-21-2014, 08:14 AM   #11
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Yup. That is exactly the same as the BA10.

Thanks for checking
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Unread 06-21-2014, 09:08 AM   #12
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After reading up on the NP207, I think that's what this adapter is designed for. Seems they all have either a 2.1" or 2.3" input gear.

My options seem to be these:

Pull the tranny and get the Novak adapter - $$

Find an NP207 and run that - no SYE available but hack and tap might be an option.

Build an oil seal extender and run the short 21 spline. That would only give me about 1" of spline engagement which concerns me a bit. Opinions?

Thanks

Last edited by T800; 06-21-2014 at 10:59 AM..
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Unread 06-21-2014, 10:57 AM   #13
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you don't really want a 207...that would be a step backwards in strength
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Unread 06-21-2014, 11:24 AM   #14
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Quote:
Originally Posted by crackedcornish View Post
you don't really want a 207...that would be a step backwards in strength
Yeah, not a great option.

I read that minimum spline engagement should be 1.5x the minor diameter which is 1.5" in this case. 1" won't cut it.

Looks like I'm off to Novak ...

For anybody that finds this thread in the future, the AA 50-7501 should NOT be considered for the NP231, only the NP207 unless you are damn sure you have the mythical 2.1" 21 spline input gear (I don't think it exists ).

Thanks for the help, guys.
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Unread 06-22-2014, 11:08 AM   #15
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The info above may not be correct. After more research at Novak, they state that their shafts will work with a long or short input gear. If a short gear is selected they will install an "oil seal spacer sleeve" in the adapter. A short gear on their setup will end up with the same engagement I'll have on the AA.

I have a buddy who is a mechanical engineer. I'll ask him to work out the engagement strength, but for now I'll build a seal extender on my lathe when I get some 3" stock and give it a whirl. If it breaks it breaks - I'll be no worse off than I am now.
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