91familyxj

I was wondering what the difference was between the 242 and 231 t-cases are? I have a 242 J in my xj now and I have a 231? I belive thats what it is it is out of a 88 2dr. They are both on an auto tranny. So I was just wondering what the differences were and if they are interchangable? Thanks

winston427

They are intechangalble. The 231 is a part time TC and the 242 is full time. The 242 can used in 4wd drive on pavement without damaging the internals. I'm sure someone else will be better able to give a more detail description.

Cherokee 4.0

my descripton is the 231 is better than the 242. Period. Unedumacated info right there.

mike37

keep the 242 it is better than the 231 from the 88 and if you wanted to swap them you would need to change the input gear on the years you have the spines wont match

91familyxj

ok cool I didnt see a real problem with changing them but it never hurts to ask. The 231 is still hooked up the the tranny just sitting there untill the day comes and my tranny or tc fails. But all and all the only differance is the 242 I can drive on the streets in 4 wheel drive and it not break?

2000xj

With the NP242, you can drive on any sort of terrain in 4-Full-Time because this allows the front and rear tires to spin at different rates (48% of power to the front, 52% to the rear). Other than the Full-Time option, the Part-time and Neutral settings work just like they do in the NP231.

Six-Pack Smile

naw man i have hade both transfer cases, and the 231 was like a bigger spline than the 242 and the older ax15 tranny, but i like the 242 they are NOT full time but they can be, they have very good selections for diffrent driving conditions, and they still got the lower crawl ratio in 4lo that the 231, when out wheeling. i have a 231 and tansmison sitting in my yard because i will probably blow my 242 up so i just swap that tranny and transfer case. because they are not interchangeable. i grenade the chain on my 231 once right out of the side housing on a t-case lol.

mike37

your info is all wrong it depends on year and trans that was bolted to the tc
there are two spline sizes and three input shaft length
pre 90 all have the small spline except for the ones bolted to the ax15

Six-Pack Smile

mike i said ax-15 and i said older trannys and t-cases my info is shotty, but true dude.

2000xj

The NP242 does not have a lower crawl ratio than the NP231... both of the them have a 2.72:1 Ratio in 4Lo.

The NP242 is actually rated to take more torque than the NP231 can as well.

The NP242 and NP231 are interchangeable depending on what the input spline count is on the tcase. They were either offered with a 21-spline or 23-spline count on the input for the tcase from the trans.

91familyxj

So you guys say the spline is different but what about if it is aready on a tranny. All auto trannys are the same right? (well not if some rebuilt the insides) but all and all the same?

mike37

not all the pre 90 aw4 have 21 spline the later ones have 23 spline

91familyxj

So the new ones are a little stronger. My back up is out of an 88 and my truck is a 91. Should there be any problems putting a 88 dr. tranny and tc in my 91 4dr. is that drive shaft longer in one of then or are they the same.

mike37

yes you can swap trans and tc as a package they are the same size
you may need to swap the plugs for the tcu and nss I'm not positive on that part

the older trans is the week part
if you want to keep the newer trans you can swap the input gear on the tc to make the old tc fit the new trans

BuckB91XJ

So long as you only let your heavy right foot get the best of you when you are on a slick surface the AW4 and TC that you currently have in your Jeep should live a long life....it is always good to have back-up parts, though, when your wheeling rig is also your daily driver.