NP 231 Input shaft Tech TJ/YJ/XJ/ZJ/MJ

#1
So whenever you ask someone about input shaft differences on a 231 you usually get a mention of spline count; either 21 or 23 spline, while some will mention lengths without knowing much concrete info.

I have been doing some research and figured I would consolidate it here to help with other peoples swaps.

Info is from advance adapters and Novak.

Short Input 21 Spline
AW4 (through 1990)
AX4
AX5
Peugeot BA 10/5 (earlier)

Short Input 23 Spline
Earlier (pre-'95) AX15

Long Input 23 Spline
Later (post-'94) AX15
TF904
TF999
Peugeot BA 10/5(later)
NV3550
NSG370

Medium Input 23 Spline
46RE Jeep ZJ's '93 to '95 only
AW4 (post-'90)


Input Gears and Compatibility
Hold on to your seat...
The important variations to look for in the 231 transfer case are in the input gear. The 231 comes in 21 spline and 23 spline versions with long, medium (rare) and short variations.
The long shafts protrude 2.1" from the front mounting face of the transfer case. The short version protrudes 1.2". The rare medium shaft protrudes 1.7". You should be careful when swapping any of these gears due to different bearing widths and gear teeth. The following chart shows how to determine which input gear you might have by transmission. It is always recommended to verify first hand if possible.



Because of differences in the cut of the gear, as a general rule, one should not interchange 1987-1993 gears with 1994-present gears. These years are not always hard and fast delineations. If one is not absolutely certain, disassembly and inspection is required.
Note that some transmissions change spline count. The Peugeot BA10/5 had both 21 or 23 splines. The AW4 had 21 splines through 1990. In 1991 (the same year the 4.0 HO was introduced) the AW4 splines increased to 23.







I'm still a bit unsure about the medium length shafts as they say all post 1990 aw4s come with them, but they say they are rare, which is wierd. I'll update with more info as I find it.
 
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