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  #1  
Old December 6th, 2016, 09:55
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Overland Overland is offline
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AX5 interchange between early and late

Greetings fellow four wheelers.

I had the occasion of replacing the transmission in my 96 XJ with one from an 86 behind the 2.8. I can report that after swapping the bell housing, it bolted up just fine with my original clutch and release hardware.

I had no trouble swapping the bell housing, but at the time my understanding of the transmission was minimal and it was getting late. While my NP231 splined up to the early transmission and bolted up, the input gear seal landing never reached the seal. This was due to the combination of a short shaft in the 231 and a deeper recess in the early AX5 case flange. I bolted the old NP207 back on and used the early driveshaft.

Now, rather than downgrade to the 207 and live without a speedometer until I can rebuild the original, I had the idea or replacing the back half of the transmission case with a period correct housing. I've read instances of people servicing fifth gear in-situ so I know it can be replaced without removing the transmission by following the back half of the disassembly procedure. What I don't know is if the output shaft is the same length from the mid plate.

I know the 207 flanged up easily to the late transmission, but I'd hate to go through the work getting to it only to find out that my case stops a fraction of an inch short of the flange once swapped. Or worse, it slides together easily but binds once torqued down.

I'll find out through trial and error, but I'd appreciate any input from the more experienced community here. Ski season is here and I don't want to miss any of it because of the 207 shaped spacer between my transmission and rear driveshaft.
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  #2  
Old December 6th, 2016, 10:06
RCP Phx RCP Phx is offline
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Re: AX5 interchange between early and late

You have the idea backwards, you need to install a longer input gear on the x-case. I don't believe you can change the transmission output shaft without total dis-assembly.
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  #3  
Old December 6th, 2016, 10:22
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Re: AX5 interchange between early and late

Case, cover, what have you. The output shaft is the main shaft and there is no changing it short of complete disassembly. This is well established.

I might add, I have one of these on a jig to be rebuilt so the internals are no mystery. The two I have to build one from are both late models so I have no early model to look at short of disabling my present driver.

If someone had an early trans and could measure the shaft from the fifth gear lock ring, that would tell me pretty much everything I needed to know. I'm fairly certain that everything in the rear case half interfaces the same.

Just for clarity, my goal is to swap the rear case half on the trans for the late flange and seal position. I don't believe a 231 21 spline long input shaft is available for purchase.
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  #4  
Old December 6th, 2016, 10:25
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Re: AX5 interchange between early and late

I guess I could pull the transfer case off and stick a tape up in there before I split the transmission housing.

There's also some chance that the case changed slightly with changes in fifth gear and its shift fork. Between the two I have out, the forks are different as well as the end of the countershaft.

This is all very fascinating shit from which someone may benefit in the future.

Last edited by Overland; December 6th, 2016 at 10:41.
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  #5  
Old December 6th, 2016, 11:01
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Green Mesa XJ Green Mesa XJ is offline
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AX5 interchange between early and late

Um, why not find a 87-90 231?

Np207 is strong enough but no parts support and the speedometer gearing is odd ball gm reverse direction with no real way to swap it to more jeep standard stuff. I've heard of plenty of guys with early 4cy and 2.8 dealing in a 231 with 21 spline, 87 to 90 I think.

There is something different about the early ax5, while reading and watching videos about how to rebuild them there was mention of how some things are different in the early ax5 and to be sure to buy the right kit. I don't remember the specifics but it made the early ax5 seem slightly stronger.

Btw I wouldn't try to disassemble the transmission in car, watch a video on it too many small parts to lose and I don't think you'll be able to easily swap the part you want to any way.


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  #6  
Old December 6th, 2016, 11:12
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Re: AX5 interchange between early and late

I have the service manual for AX5 and have opened two of them on the bench. Small part removal is part of the service procedure so if done right, nothing falls out but oil. It's not much more involved than removing the transfer case, and if it doesn't work, I'll simply put it back as it was and fill it up again.

If it does, I'll drive away with functional four wheel drive, electronic speedometer, and the knowledge that I can rebuild the original at my leisure, perhaps in the spring between ski season and wheeling/camping/travel season.

Why buy something when I may have everything I need?

The 207 requires a disconnect front axle and related vacuum control system. I have all of this, including the shifter, drive shaft, etc. It can stay in the 86 where it's at. To commit to a downgrade so involved is entirely out of the question.

The 86 was a daily driver until it donated its transmission. Fuel injection won.
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  #7  
Old December 6th, 2016, 11:33
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AX5 interchange between early and late

Well I've seen quite a few of the old 231s go for cheap, seems like everybody wants the 23 spline, seemed like a easy way to bolt it up and get going.

But if you've got experience then there's not much of an incentive to screw around with buying anything.

But I don't think you'd need to swap all vacuum control crap to make the 207 work, swap the front drive shaft output yoke to the newer style and either ignore the vacuum switch or swap in a later switch with the plug, but I'm not sure what the differences are with later 231s they might not use that spot in the case for the switch, I know 91-95 some 23 spline do.

I do know the front output yoke swaps 231 to 207 because if you lift the old xj you got to source the yoke and front drive shaft from a newer year.

It will be a good write up when you get it sorted. Definitely be useful to some else at some point.




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  #8  
Old December 6th, 2016, 12:16
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Re: AX5 interchange between early and late

As far as I know, the 207 is in part time high all the time. Shifting to part time ports vacuum to the front axle rather than actually shifting anything. There's a reason it didn't remain in production long, I'm sure.

For future reference, the late model shafts measure just about 6" from the face of fifth gear to the end of the output side. Case dimension from mid plate to transfer case flange is 6 3/4".
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  #9  
Old December 6th, 2016, 12:23
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Re: AX5 interchange between early and late

Just slipped under the two door and the early case measures 7" from mid plate to flange. I think the majority of the difference lies in the milling for the seal and the shaft is probably close enough.

If I wanted to be told I was stupid and lacked proper tools, I would consult the Haynes manual.
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  #10  
Old December 6th, 2016, 12:52
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AX5 interchange between early and late

Quote:
Originally Posted by Overland View Post
As far as I know, the 207 is in part time high all the time. Shifting to part time ports vacuum to the front axle rather than actually shifting anything. There's a reason it didn't remain in production long, I'm sure.

For future reference, the late model shafts measure just about 6" from the face of fifth gear to the end of the output side. Case dimension from mid plate to transfer case flange is 6 3/4".

The 207 supposed to have the same vacuum harness and switch as the 231, but it's odd ball junk for the most part. Although i never had a issue with it, doubt the 2.8 has enough power to break it or the ax5.

207 operates like the 231 far as 4wd, it's just weaker parts except for the chain. It's the HD 231 chain.
Those damn 207 speedometer gears are such one offs, I've never been able to find parts for it and it'll never work with the xj electronic speedometer gears.
I'm going to swap a 231 in the 207s place for a ton of reasons. But can't say it failed me.


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  #11  
Old December 6th, 2016, 13:30
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Re: AX5 interchange between early and late

I'm sure it's a fine case in its original configuration, but it was not my intention to end up with it over the 231.

Vacuum is not applicable to the 231, maybe you're thinking of the 229?

Since nobody has told me why it won't work, I'm about to go find out for myself.

Fun stuff.
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  #12  
Old December 6th, 2016, 13:32
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Re: AX5 interchange between early and late

Also, once I organized the vacuum system and advanced the timing, the 2.8 was pretty surprising. Fun, but it would never last with my foot.
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  #13  
Old December 6th, 2016, 14:32
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AX5 interchange between early and late

My 2.8 was/is a high altitude set up. But it was gutless going up any kind of real incline, or up to speed on the highway at sea level. Put in a Weber carb that helped a lot, then cleaned up the rats nest of vacuum lines a little. I know my motor is played out probably over 300k on the jeep frame not sure if the motor is original but it has refused to out right die. So I'm going to put it and rebuild the engine, swap the transmission, transfer case set up with something more versatile. Your 2.8 must have had real some life it, everybody tends to complain that the 2.8 sucks.

Not sure about the 229, on the 207 and 231 all the vacuum is for the CAD, in the older designs there is a place in from for a vacuum switch, some 91 but 92-95 cases I got the have the same spot in the case except with a electronic switch.




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  #14  
Old December 6th, 2016, 14:44
Jeep Driver Jeep Driver is offline
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Re: AX5 interchange between early and late

No doubt you'll do as you please............that said-


This will be my fourth AX5 in five years, and it will be the last.

I cannot speak to the 84-86 years, but, the 87-06 are all the same. '94 up for the external slaves.

I need to get my MJ rolling with the new engine, so this AX5 will go in for a short time. I'm already looking for the Dakota bell and looking for a AX15 or the NV3550. I'll lose the Hurst shifter, have to shorten the rear DS and lose the new Tom Woods front DS, swap will cost me over $2K.


Whatever you do with the AX5 will be a waste of time and money.

I learned the hard way too.


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Old December 6th, 2016, 14:59
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AX5 interchange between early and late

Quote:
Originally Posted by Jeep Driver View Post
No doubt you'll do as you please............that said-





This will be my fourth AX5 in five years, and it will be the last.



I cannot speak to the 84-86 years, but, the 87-06 are all the same. '94 up for the external slaves.



I need to get my MJ rolling with the new engine, so this AX5 will go in for a short time. I'm already looking for the Dakota bell and looking for a AX15 or the NV3550. I'll lose the Hurst shifter, have to shorten the rear DS and lose the new Tom Woods front DS, swap will cost me over $2K.





Whatever you do with the AX5 will be a waste of time and money.



I learned the hard way too.






You can literally see the difference in the ax15. Its a different version of the Supra R154, which can take a lot of power.

I lucked out finding a Dakota bellhousing, it was listed on eBay as wrangler 4cy ,they had a picture of it and the part # so I grabbed it quick. Hitting the junk yards didn't work, I found two online for a decent price, they were sold before I could pick up the phone. Probably a ebayer flipping them.
Got a 89-90 ax15 from a junkyard up north clearing out old inventory. Rebuilding a 91-92 231 to put behind it. Just got to get the time to get it all done.






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