NP231J input shaft—AX15 vs NSG370

freedom_in_4low

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I want to move my SYE over from my TJ to my LJ. Since it was just installed, including some new seals and a new chain, I'd like to just swap the cases rather than splitting them both.

As far as I can tell they're both 23 spline, but not finding much info on the length. The parts lists for a '99 and for an '06 have different part numbers. The Novak guide says the NSG370 takes a long input and the AX15 takes a short, but the case that came with my AX15 has a long shaft, so now I don't know what from the Novak guide can be trusted.

I realize I can pull the cases and find out, but I'm trying to plan ahead to minimize the time they're both disabled and blocking the garage.
 
I want to move my SYE over from my TJ to my LJ. Since it was just installed, including some new seals and a new chain, I'd like to just swap the cases rather than splitting them both.

As far as I can tell they're both 23 spline, but not finding much info on the length. The parts lists for a '99 and for an '06 have different part numbers. The Novak guide says the NSG370 takes a long input and the AX15 takes a short, but the case that came with my AX15 has a long shaft, so now I don't know what from the Novak guide can be trusted.

I realize I can pull the cases and find out, but I'm trying to plan ahead to minimize the time they're both disabled and blocking the garage.
Novak is a great company...

Notice they clearly state in parentheses...

Be certain, in any interchange situation, that you select the right length of input gear for the factory style transmission being used; e.g., a long input gear against an AX15 (usually requiring a short input gear) will cause interference at the end of the splines and put damaging thrust pressures on the transmission mainshaft and transfer case input gear.

I take that as the AX15 usually has the short input gear but not always.

Visual verification can never be wrong.
 
Novak is a great company...

Notice they clearly state in parentheses...

Be certain, in any interchange situation, that you select the right length of input gear for the factory style transmission being used; e.g., a long input gear against an AX15 (usually requiring a short input gear) will cause interference at the end of the splines and put damaging thrust pressures on the transmission mainshaft and transfer case input gear.

I take that as the AX15 usually has the short input gear but not always.

Visual verification can never be wrong.

I actually went through the long-shaft AX15 thing back in February when I did my SYE. Here's the thread where I felt like I was taking crazy pills because I had a 231 from my 99 TJ AX15 and one from a ~97 XJ AW4 and that Novak guide was wrong about both of them (and I actually posted a screen grab of that exact passage you quoted). I don't know what their basis is for that info; maybe at some point earlier in the life of the AX15 they changed how far the splines went up the shaft.

I just need to know if it's right in saying that the NSG370 takes a long input. If it does, I should be good to go because that's what I have.
 
so...has anybody with an NSG370 had their transfer case out and paid any attention to the length of the input gear? @rraulston, I think yours is a 241 but were you able to find out anything when you were considering an AX15 swap?
 
The 241 ONLY came with a short input. They didnt have different nsg370s for rubicon/non rubicon.
 
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I am 99% positive both the ax15 and nsg370 in a TJ use a short input.

I am 100% positive that my ax15 uses a long input, which means the NSG370 using a short input is bad news. And of course the one part that needs to change would be the one that requires the case be torn completely down to replace.

I'm really not looking forward to cleaning all that gray RTV off the case half flange, or getting the stock case apart without destroying the output housing. Just swapping the cases would have been sooo easy. The problem of course is that I have a 2 car garage, and a wife that's not keen on cleaning the snow off her car in the morning in a place that gets almost 10 feet of snow each winter. Where pulling both cases and getting one put back in to pull the TJ back out of the garage would be easily doable, it's a much bigger task to add tearing both down and reassembling one to the scope.
 
You could leave both tcases installed and just swap the SYE parts. Sounds like a day job or weekend job at best.
 
Looking at the picture you posted in this thread:

https://wranglertjforum.com/threads/long-np231-input-gear-on-an-ax15-transmission.30744/
Despite you having a long input 231, you can see that the seal rides very close to the tcase.

agreed. If the NSG370 uses a short input then I'm sure the seal location probably isn't dramatically different between the 2. But the idea of the input gear overreaching the extent of the output splines on the NSG370 is a concern.
You could leave both tcases installed and just swap the SYE parts. Sounds like a day job or weekend job at best.

That's probably what I'll do. I much preferred doing my SYE on the bench but not having to mess with the t-case mounting bolts or the input seal carrier will save some time, even working underneath the rigs.
 
I am 100% positive that my ax15 uses a long input, which means the NSG370 using a short input is bad news. And of course the one part that needs to change would be the one that requires the case be torn completely down to replace.

I'm really not looking forward to cleaning all that gray RTV off the case half flange, or getting the stock case apart without destroying the output housing. Just swapping the cases would have been sooo easy. The problem of course is that I have a 2 car garage, and a wife that's not keen on cleaning the snow off her car in the morning in a place that gets almost 10 feet of snow each winter. Where pulling both cases and getting one put back in to pull the TJ back out of the garage would be easily doable, it's a much bigger task to add tearing both down and reassembling one to the scope.
Not sure about the shafts. But I noticed you referenced Grey RTV on your case halves. You should research anaerobic gasket maker for sealing two metal halves. I believe its what comes from the factory when these are sealed new.... Just a thought...
 
Not sure about the shafts. But I noticed you referenced Grey RTV on your case halves. You should research anaerobic gasket maker for sealing two metal halves. I believe its what comes from the factory when these are sealed new.... Just a thought...
Grey rtv is what was recommended in the FSM for my 99 so that's what I used when I installed my SYE in February. Haven't looked into my 06 yet but I'm open to whatever is best. I haven't found a sealant of any color that is enjoyable to remove so I'm not sure it matters much as long as it doesn't leak.

Being that your last nsg370 rebuild video is a month old I take it yours is already back together?
 
Grey rtv is what was recommended in the FSM for my 99 so that's what I used when I installed my SYE in February. Haven't looked into my 06 yet but I'm open to whatever is best. I haven't found a sealant of any color that is enjoyable to remove so I'm not sure it matters much as long as it doesn't leak.

Being that your last nsg370 rebuild video is a month old I take it yours is already back together?
I have the transmission together and waiting on the engine from the machine shop. I put new lifters on an old camshaft when I did a valve job due to #1 exhaust valve not seating. Got 25 miles and destroyed them all! Yes yes, I know the rule of thumb, but thought I could get at least 1k miles so I could Jeep through the winter and do a summer rebuild. I've used new lifter old cam combos and have gotten 10k miles before. Not this time....Sucks. Over 2k in my new trans and I'm sure 3k in the engine..... The new head/valves/springs/lifter and cam are (guessing) $1200 + -. cant wait to get the bill......o_O
 
We take gambles to save ourselves time or money, and sometimes we lose. I've enjoyed your transmission rebuild videos, thank you for being the trailblazer and documenting the journey!
 
I have the transmission together and waiting on the engine from the machine shop. I put new lifters on an old camshaft when I did a valve job due to #1 exhaust valve not seating. Got 25 miles and destroyed them all! Yes yes, I know the rule of thumb, but thought I could get at least 1k miles so I could Jeep through the winter and do a summer rebuild. I've used new lifter old cam combos and have gotten 10k miles before. Not this time....Sucks. Over 2k in my new trans and I'm sure 3k in the engine..... The new head/valves/springs/lifter and cam are (guessing) $1200 + -. cant wait to get the bill......o_O

if you haven't mounted the transfer case to the back of the transmission, would you mind taking a couple of measurements for me?

1. How far the output shaft protrudes beyond the mounting face on the back of the NSG370
2. How far up the output shaft could an input gear go, either from the end of the shaft or from the t-case mounting flange.

Even if 241's were all short-input, it's not immediately apparent to me (based on these screenshots from your last build video) that a long-input 231 wouldn't work. The AX15 output has a consistent diameter with the splines machined into it, whereas the NSG370 looks like it has a reduction in diameter that the splines seem to just disappear into. It seems like if the input gear went past the splines it shouldn't thrust load the shaft unless maybe it got all the way to that machined journal area.

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Looks like the nsg370 output shaft seals the output shaft seal. Other transmissions rely on the transfer case input to seal the output shaft seal. Those are the instances where short vs long input are critical. The nsg very well might bolt up to either input after seeing that picture.
 
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if you haven't mounted the transfer case to the back of the transmission, would you mind taking a couple of measurements for me?

1. How far the output shaft protrudes beyond the mounting face on the back of the NSG370
2. How far up the output shaft could an input gear go, either from the end of the shaft or from the t-case mounting flange.

Even if 241's were all short-input, it's not immediately apparent to me (based on these screenshots from your last build video) that a long-input 231 wouldn't work. The AX15 output has a consistent diameter with the splines machined into it, whereas the NSG370 looks like it has a reduction in diameter that the splines seem to just disappear into. It seems like if the input gear went past the splines it shouldn't thrust load the shaft unless maybe it got all the way to that machined journal area.

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