98 242 into 91 w/231

88 Wagonman

88 Wagonman

New member
Let's get this out of the way: I seached and seem to suck at it. Please help. Ok now to the tech:

I have a 91 XJ aw4 NP231 C8.25. I want to switch to a NP242 and I know it's possible. My question is, can I put one in from a 98 as long as I grab the rear driveshaft? I will grab the shift gate and bezel from the JY, and I know that I will have to use my speed sensor and wire the indicator lights. Anything that I am forgetting about? TIA guys.
 
M

Mr. mud

New member
Ummm... no. The spline count on the transmission output shaft is different. Your 91 is a 21 spline, and the 98 is a 23 spline. Look for an older 242 out of an xj the same age or loder than yours.
 
F

fubar XJ

New member
From what I've read, '91 was a transitional year. Depending on the month of manufacture or even the parts on hand for that particular build-lot, you could have either a 21 or 23 spline output. My '91 has a 23 spline output, Sept. build date.
 
88 Wagonman

88 Wagonman

New member
Thanks for the replies guys. I guess I just assumed that ALL 91 and up were 23 spline. Maybe we need to edit woody's writeup in the FAQ? According to that writeup 87-89 is 21 spline and 90-01 is 23 spline. What's the best way to find the build date?
 
ehall

ehall

NAXJA Member
NAXJA Member
If your 91 came with a 231 you should be able to look for vacuum disconnect parts to determine if it's from the AMC production. No disco==23 spline.
 
88 Wagonman

88 Wagonman

New member
ehall said:
If your 91 came with a 231 you should be able to look for vacuum disconnect parts to determine if it's from the AMC production. No disco==23 spline.
Click to expand...
I know that the axle is a non-disco. I didn't even think about that, thanks.
 
L

lil_red_wagon

New member
just have to add mine is a 90 and it came with a 242 it is a 21 spline. i had to have the linkages too when i changed from the 242 to the 231. there will be a build date on your tc on a lil round plate on the back of it.
 
88 Wagonman

88 Wagonman

New member
Ok, got the swap done, everything works great! When I was searching, some things that I kept coming across that did not give specific answers:
1) Are the shift gates the same? No they are not, you must change them.
2) Are the linkages the same? They are the same except for the length of one rod, although I suggest changing them all if you have them.
3) Indicator light switch. This proved to be difficult to find info on. The 98 242 has a four pin switch and the earlier model either had a vacuum switch or two switches with two pins each. I ended up making a custom plug and play harness using parts from a 92 XJ and an unknown year ZJ.

The end result came out very well and it works as well as if it came stock with it.
 
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