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Np242 Differences

Crusher16

Crusher16

RRC President
NAXJA Member
Location
Richardson, TX
I just picked up an NP242 from a '99. I'm planning on swapping it into my '91 which also has a 242.

Are there any differences that might cause problems? I think I noticed that the tail housing is different.
 
the tailhousing is indeed different. You need the driveshaft from the 99, or you can swap parts from your 242 to the new one to make it work.
The internal case dimensions and all that jazz are the same. The input gear should be the same.
 
I thought the 91's are 21 spline output on the tranny unless its a AX15? I know for sure the 99' 242 T-case is 23 spline input.
 
For the most part 90 could be either 21 or 23-spline. So 91 should be 23-spline.
 
Thanks guys. I stretched the chain in my '91. Guess Ill just swap the chain over from the '99 to the '91 since I don't have the driveshaft from the '99.


EDIT: or wait, could I just swap tail housings?
 
Last edited:
You could swap tail housing, yeah.


The difference between the two is not really in the shaft, but in the way the Slip yoke is lubed.

96 and newer uses grease inserted into the splines of the slip yoke to give it the lubrication it needs to function. Where as with the 95 earlier slip yokes, they get their lubrication from the ATF in your T case. hence the different tail housings.

If you are that concerned about it, swap out the tail housings. It will be just fine to do so. otherwise, you are gonna have to find a rubber boot to protect the slip yoke if you use the later tail housing.
 
Crusher16 said:
Thanks guys. I stretched the chain in my '91. Guess Ill just swap the chain over from the '99 to the '91 since I don't have the driveshaft from the '99.


EDIT: or wait, could I just swap tail housings?
Click to expand...
swap the housings, the mainshaft is identical, just the housing and seal changed.

as to the 21 vs 23 spline arguement, I believe that ALL HO outputshafts are 23 spline. the 21 spline thing was just an AMC/Renix thing.
 
Awesome. Good info. Thanks guys.
 
Crusher16 said:
I just picked up an NP242 from a '99. I'm planning on swapping it into my '91 which also has a 242.

Are there any differences that might cause problems? I think I noticed that the tail housing is different.
Click to expand...
if the 91 is a h.o and the 99 is a h.o its good to go. also the only difference is in the tail shaft is one is a wet seal 96 or older.. newer being dry everthing alse is the same ie drivshaft will bolt right in
 
So we swapped tail housing with the one from my 91s to the 99s. I don't believe that the main shafts are the same length. Got the 99 242 with the 91 tail housing setup with the re1801 hack n tap but the silver flange does not reach the seal on the tail housing.

Pictures in a minute.
 
IMG_20101024_181206.jpg


IMG_20101024_181221.jpg
 
And here's what it is suppose to look like. :(

hackntap2.jpg
 
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