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90 XJ t-case input splines

1990JEEPXJ

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San Diego
seems like 90 was the year that some stuff may work in newer XJ's or they may not, a transition year. so what was the spline count on the transfer case input shaft? i have read on here both 23 and 21. i want to know from someone that has first hand knowledge with a 90 xj. my 242 is shot and is my DD so im just looking to replace the case and not rebuild the 242
 
If you have an NP242, you should have an AW4. As I recall, the spline change for the AW4 ran around 1991/1992 (vice the 21sp to 23sp change for BA-10 to AX-15,) so you should still have a 21-sp case.

However, you can always just swap the input gearset, if yours is still in good condition. I recall that the input gear helix angle was changed around 1994/1995 (not so much that they still won't mesh, but they won't run together...) so try and score a case made before 1994, just in case (this applies primarily to the NP231, but I'm not sure about the NP242. And, I haven't gotten a line of comms open with New Venture Gear yet...)
 
yeah i do have the AW4. im not 100% set on getting a replacement. if rebuilding it is quick and easy then i dont mind that. its just my DD so it cant be out of commission too long. my transfer case still works, but the chain is stretched and rubbing the case, and it leaks like crazy from the front output. it also has a hack 'n tap on it.
 
While I haven't done the job (yet...) I've been through the manual - if you're reasonably experienced and skilled mechanically, and you make sure you have everything beforehand (overhaul kit and any special tools,) I don't see much reason why you couldn't get the thing done in a week-end.

Nota Bene - If you decide to DIY, loosen the output yokes before you pull the case. Put it in 4L, block the wheels, and use the weight of the vehicle and whatever leverage you can get to break torque on those nuts. Overhaul, install the case, then put in 4L and block the wheels to use the weight of the vehicle to torque those fasteners - you're looking at something like 200 pound-feet or so...
 
i have no problem going ahead with a rebuild. seems like a better idea considering if i replaced it i would need an old transfercase in an unknown condition from the JY, which may need a rebuild anyway. the only specialty tool would be some snap ring pliers right? i was just wondering if i were to go ahead and to the JY case, what spline count would i be looking for? i see a lot of mixed info.
 
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Yes, I too am confident that you have a 21 spline output on the AW4. I believe the change was with the H.O. engine, so 91+ is 23 spline.
 
If you have an NP242, you should have an AW4. As I recall, the spline change for the AW4 ran around 1991/1992 (vice the 21sp to 23sp change for BA-10 to AX-15,) so you should still have a 21-sp case.

However, you can always just swap the input gearset, if yours is still in good condition. I recall that the input gear helix angle was changed around 1994/1995 (not so much that they still won't mesh, but they won't run together...) so try and score a case made before 1994, just in case (this applies primarily to the NP231, but I'm not sure about the NP242. And, I haven't gotten a line of comms open with New Venture Gear yet...)
I am fairly certain it was 90 to 91 or midyear 90. Checking the chrysler book of lies shortly...

I would put money on it being a 21 spline. You can swap the input gear on the TC as noted though, so just make sure you get one with the same gear cut like 5-90 said.

This is why I like sticking with 91 and later tranny stuff, there is much less variation. Things will in most cases just bolt up, though other minor parts may need to be changed.

One of these days I need to put together an all-encompassing bar chart that shows what changed and when. I have most (hopefully, constantly running into new info though) of it in my head but it gets kinda mindbending to try to put it to paper. I know of changes from 86-87, 90-91 (or 90-90.5), 95-96, 96-97, 97-98 in the case of automatics, and 90-91 (or 90-90.5) and 94-95 in the case of standards. I refuse to learn anything about pukegoats because they are not transmissions, they are ticking time bombs, so they are not listed :spin1:
 
If you can see the 8 digit Chrysler part number on either the transmission or the transfer case, and the serial number off the transmission, I can tell you for sure.

Transmissions serial number 131163 and earlier are 21 spline (in XJs and MJs) while transmissions serial number 131001 and earlier are 21 spline in YJs. 131164 and later (XJs/MJs) or 131002 and later (YJs) are 23 spline.

Looking at the page for the transfer case year splits makes my head explode. There are different listings for various combinations depending on XJ/MJ/YJ, 4cyl vs 6cyl, 5spd vs auto vs peugeot, 87-89 vs 90, 231 vs 242, with different exact build date splits for each. It is truly mindbending and there are something like 28 listings, some with different and conflicting/duplicate part numbers. I'm not even going to try and interpret it because I know I'll get it wrong. The serial number is probably the most reliable "book" method of telling you which you have, short of going back in time and entering your VIN into AMC's computer database, but the one true way of really telling for sure is to pull the damn thing apart and count.

Built in may 90 *looks* like it might actually be 23 spline but I'm honestly not sure. Most of the build date splits are on various days in october and november of '88 (wtf?) and '89. The real problem is that model years and year of manufacture are nowhere near hard and fast and overlap in strange ways.
 
Good question :dunno:

My bet is that it will be stamped into the badge on the transmission. On an AW4 the badge is on the passenger side right above the pan somewhere, seem to recall it being near the tail end.
 
well i found an aisin warner badge near the back of the transmission just above the pan on the passenger side. the number is 90 D 51618. not sure if that can tell you anything but i will keep looking for other numbers elsewhere.
 
and the only marks i could see on the transfer case were on the tag itself. not sure what can be deciphered from that but the number on that is 5300 8223
 
Excellent... that tells me a lot actually.

That cross refs to an NPG 242 transfer case, to be paired with an automatic transmission, in a 1990 model year XJ or MJ built after 10/16/89*, which matches up well with your 5/xx/90 build date.

So without counting the splines, I would think that this will be a 23 spline case.

Of course someone could have swapped it in at a later date, before you bought it, and swapped a 21 spline input gear into what would normally be a 23 spline case. Used vehicles can't really be trusted to tell the full story when comparing to a parts catalog.

* this is the build date split for this engine/model year/transmission/transfer case configuration only... they switched over on different days based on when they ran out of the old 21 spline units configured for each drivetrain setup, then wrote down what dates the switchovers occurred on.
 
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