AX15 & NP231

I've searched and read many posts relating to my topic, but none really answered my question. I have an 89 Renix MJ that I am swapping over to HO. Found junkyard HO MJ engine and interior wiring harness.

My 89 has the AX15/ 231 combo. From my research online and in the Jeep parts manuals...My 89 AX15 is the same unit/ part# as they installed in 91 HO MJ's. My 231 is obviously getting tossed for a 91 transfer case. But, here's my question: Is my current 89 231 a 23-spline because from what I can tell according to the Jeep parts manuals it is a 21-spline case; however, most websites (including Novak) say that AX15's always have a 23-spline case behind them no matter what year? Any insight of what's the truth?

Finally, assuming my current case is a 23-spline, I'm guessing my 89 AX15 would have no issues bolting up to a newer 231 (91 or 92 XJ era)?

Thanks

I have an 89 with the ax15 manual as well. From my reading I think its 21 spline. Read through this long post there is some experiences to back up that early ax15's were 21 spline and internal slave cylindar.
http://www.naxja.org/forum/showthread.php?t=70388
Recently I had the clutch replaced at a shop and they told me I have the peugeot becuase of the clutch parts they had to order - basically the same clutch that would have gone in the peugeot I think. I know for sure that I have the ax15. So when I read the above thread it made sense. I think around '93 the ax15 went 23 spline? Being an 89 I think it safe to say 21 spline.

reread a bit of the thread again ... looks like the cutover year for the ax15 from 21 to 23 spline may be 90 or 91, not 93. My experience with the clutch shop and that thread has just about convinced me we probably have 21 spline in the 89 ax15. When I go to the Tera-lo 4:1 kit I will disassemble first and count the darn splines to confirm.

Thanks for the reply.

I've confirmed the same part#53008209 transfer case was used from 89 - early 91 in the XJ/ MJ. I've also confirmed it's 21-spline. 23-spline was offered after Feb 1991 build (52097522). This obviously crosses over the Renix/ HO threshold. From vac TC switch to electric. Chrysler/ Jeep sells one transfer case for this model year span. Do you know if it's an easy swap/ possible to convert from a vac 231 to electric?

I wonder what I'd end up with (elec or vac) if I ordered a remanufactured unit 53008209 (now badged R3008209)?

I am not sure what it would take to convert from vac to electric. I also did not really know what the vac did in the first place. From what I can tell the vac on the 231 controlled the discoonnect system on the D30 front axle? And possible the part time 4wd light on the dash? Read this post for these clues.
http://forums.off-road.com/jeep-short-wheelbase/103364-np231-vacuum-trouble.html
Is the vac or electric system even needed on the tcase? Since I swapped out my front disco D30 to a solid passenger side and capped all those vac lines the 4wd light on the dash has never worked but it has never mattered, as the tcase works when enganged. Is the operation of the tcase all by the manual action of the lever? I am not sure if there is still some reliance on the vac system. I am hoping it is not so I don't have the possibility of strange vac problems in the future.
Possibly reading this wrong - did the speedo operation go to electric instead of manual cable? Not sure what you would need the electric function for.

Vac is for Disco-axle and light only. There is a workaround for the light however. My guess would be you DO have a Disco 30, unless it was swapped. But there are a few things you can do to "work around this" so to speak.. A posi-lok kit (or a DYI thats similar), slide the fork over and lock it in place, swap in a 1 piece shaft/inner seal, swap an entire non-disco 30 axle, or swap in an entirely different axle if you want.