NP242 plus AX15?
 

I know some folks with an AX15 manual transmission have swapped in a NP242 transfer case for the original 231. Does the shifter end up feeling any different after the swap? Any regrets?

I'm thinking about swapping my NP231 for an NP242 to get the full-time 4WD, since my wife is going to start driving my '94 XJ more often in the rain...

I did this swap years ago. It's doable with the correct input shaft on the T-case. You'll need to change the linkages that connect the lever to the t-case.


Is it workable? Very. Do I suggest it? No.



Because of the center diff inside the 242 .... there is always some slop/backlash. It is not noticeable with an automatic, however, as you shift with a standard trans, you will hear and feel the gears loading & unloading. Will not hurt anything, but it can be a bit annoying to some people.


The 231 is a stronger case with slightly greater aftermarket support. On top of that, I think the fulltime feature is a bit unnecessary (looking back now). My wife's 97 XJ had a 231 that we drove for 276K without an issue. It's not that hard to pull it in/out of 4wd and if it's patchy traction, we would just leave it in 4wd.



IMO .. you'll gain more by sticking a 70 lb bag of sand in the cargo area.




If you have specific questions, don't hesitate to ask.


Joe

the only thing i disagree with is the 231 being a stronger case.....the 242 is damn strong. i swapped my 242 for a 231, for greater aftermarket support, and i broke the 231 first time out.

i wheeled on the 242 hard for 2 years with no problems. the 231 i swapped it out for came out of a jeep with 100k less miles than my 242.

prob just a fluke, but i beat the crap out of the 242.

aftermarket has stepped it up a bit for the 242 within the last couple of years, but parts are more expensive due to the low demand.

i havent put one behind a manual trans so im sure endlessmtnfab knows what he is talking about with the loading and unloading of the center diff.

just realized i am being a post whore this morning so i appologize....im gonna go work on my secret project vehicle!!

Bones,


I did not say the 242 was a weak case. I just said the 231 was stronger. There are "max torque" specs posted all over the web, showing the max rating difference between the 2 cases. Something like a 200 ft lb difference.


If you compare the 2 shafts, side by side ... you will notice the 242 has a slightly thinner main section to make room for the center diff and the 3426 needle bearings.


The only way to get a HD 242 output shaft .. is to pull one off the Hummer vehicles. It's a viable swap -- just not cost effective.




Joe

Sure wish I could drive one with this swap, so I could feel the slop you're talking about. Does it actually slow down shifting, or is it just a noise? The AX15 doesn't exactly have the slickest shifter in the world anyway, but I don't want to turn it into a real slushbox.

I've gotten along just fine with the 231 for 15 years and 139K of daily driving now. It's not about taking it in and out of 4WD, it's about the steering binding up. Going down the highway is no problem, but my wife isn't used to taking it out of 4HI before she makes a sharp turn in the parking lot.

I have a secondary reason for thinking about this, too. We're getting a 3500lb boat, and I'd like to be able to use the full-time system for towing and for maneuvering up the ramp.

But, like I said, I've been shifting in and out of 4HI for 15 years now, so I'll get along either way.

i know you didnt say the 242 was a weak case....just the 231 was stronger. just puting in my 2 cents.....not starting crap.

One other question, EndlessMtnFab: Was your swap vehicle lifted, and do you think it had an effect on the slop? My XJ is not lifted, it's just a daily driver and tow vehicle.

The gears in the center section will "float" because they are not tightly intermeshed. So what I am describing is simply the noise/action of the gears re-meshing to each other. An automatic trans will almost always have positive pressure on the gears as you accelerate or decelerate. However, the clutch of a manual allows complete disengagement of driveline torque (other than centrifugal rotation). That is how you feel/hear the slop I am referring to. It's the gears engaging against themselves again and it takes like a microsecond.


An auto trans always has some kind of 'positive' torque as it shifts from gear to gear (up or down). The clutch of a manual transmission allows a complete power disconnect. Add the centrifugal rotation to the lack of input torque, and you can see why the gears 'unmesh' slightly.


The 89 I did the swap on was lifted and had an SYE. However, as you can see by my explanation above, it would have absolutely no bearing the process.




Joe

Thanks for answering my nit-picky questions, EndlessMtnFab.

I think I understand--the input shaft of the NP242 has no pre-load, so the planetary gears in the center section can backlash. The automatic always has some positive torque on the drivetrain (except when dead stopped), so it can't backlash. The NP231 has a straight-through drivetrain, so can't backlash.

So this is more of a noise, than a felt bump, as the input gear catches up to the planetarys again?

A bit of both.


I really don't know how to describe the "feel" portion of it. More like you are feeling a "click" as you let the clutch out after each shift. I guess you could maybe use the analogy of how a worn chain might feel in these cases. You will still notice it in 2wd even though the center diff is not engaged. Mainly because it will still spin and you'll just feel the gears as they contact each other. Believe me .. it's nothing major. Just a different quirk you may or may not like.


I have nothing against the 242 for most situations.



Joe

Actually, that's a great description. Knowing now that it's backlash, with that description I can almost feel it. It'll feel odd, but I can live with it if I know what's going on.

I almost asked that question, but from your explanation it was clear you'd feel it in 2WD.

It would take some getting used to, but I'm pretty sure I wouldn't hate it. I'll have to think about whether the improved steering in rainy conditions, and the improved towing performance is worth the expense, trouble, and time of doing the swap when I've already got a perfectly functional 231.

Your point about the 70-pound sandbag is well taken.

Thanks much for the answers.

Neil