Transfer Case Question NP242 vs NP231

[Lost_Wrench]

New to forums, so thanks in advance for taking the time to read this and inform or educate me on these two 4wd systems.

So I have two Cherokee XJ's. One is a 1998 with (I believe) an NP242 Selec-trac T-Case. It has the part time and full time 4wd options. The 1996 has the NP231 which only has the Part-Time 4wd option.

I've owned several pre-97 XJ's with the 231 T-Case but the 98 is new to me and I am unfamiliar with it. It seems to work great in Full Time 4wd on snowpacked roads and getting up my steep snowpacked (plowed) driveway but the Part Time either isn't working properly or I'm not doing something right.

I decided to do a side by side 4x4 test of both Jeeps on a steep-ish unplowed road on the back of my property. Both Jeeps have good tires. My 96 XJ performed great and the 231 4wd system and T-Case was a beast as usual. It climbed right up and out of 10 inches or so of new snow on top of a snowpacked base with zero hesitation. 4Hi and 4Low worked as they should. The 98 XJ with the Selec-Trac didn't fare as well. In 2wd it just spun as expected, but then in Part Time 4wd it had without a doubt more traction than in 2wd (enough to eventually get me unstuck) but no where near what the 96 was capable of doing. Continuing the test in Full Time 4wd gave exact same results as Part Time, and 4low Part-Time did not feel like it was in 4wd at all, it just felt like 2wd low range. Is my T-Case in the 98 only working in Full Time mode where traction is only given to the wheel with the least traction? Like I said, it works great around the snowy county roads but in deeper unconsolidated snow forget it. "Part Time" in the NP242 should work the same as in the 231 right? So something isn't engaging correctly with my T-Case most likely? Either that or that T-Case sucks (unlikely). Any input appreciated.

Nick

[maxbraketorque]

- Does your '96 have any limited slip diffs or better tires than the '98?
- What does the transfer case status indicator light on the dash show when in Part Time 4WD?

[Lost_Wrench]

The 96 has the Chrysler 8.25 but I honestly couldn't tell you if it's an open diff or LSD. Tires are are both fairly new Goodyear Wranglers on both so that's not a factor.

The 98's 4wd indicator lights work as shown below.

Shifting into 4Hi = "Part Time" indicator light
Shifting into 4wd Full Time = "Full Time" indicator light
Shifting into 4Low = " Part Time" Indicator Light

Being new to owning a 98 is that correct? It seems like it is unless the indicator is supposed to say "Low" somewhere when in 4Low.

[Lost_Wrench]

Front axle is Dana 30 which I think is open. Maybe someone else knows for sure.

[maxbraketorque]

Originally Posted by Lost_Wrench

The 96 has the Chrysler 8.25 but I honestly couldn't tell you if it's an open diff or LSD. Tires are are both fairly new Goodyear Wranglers on both so that's not a factor.

The 98's 4wd indicator lights work as shown below.

Shifting into 4Hi = "Part Time" indicator light
Shifting into 4wd Full Time = "Full Time" indicator light
Shifting into 4Low = " Part Time" Indicator Light

Being new to owning a 98 is that correct? It seems like it is unless the indicator is supposed to say "Low" somewhere when in 4Low.

The indicator light scheme is correct. My brief experiences with my NP242 is that the indicator lights show the actual status of the transfer case. I've shifted from 2WD to 4FT and until the light shows 4FT, its not in 4FT. Anyhow, if the front and rear diffs are open, and if the TC is in 4FT, its possible to have only one wheel spinning whereas in 4PT, at least one front and one rear will always be spinning.

[Tim_MN]

Is the t-case shift mechanism properly adjusted ? Are the shift fork tabs excessively worn ?

The 242 can be a bit stubborn to change modes, especially if it is not regularly used. As already suggested, a limited slip will make a noticeable difference.

I suggested you change the fluid, and exercise it a bit.

[FernGreen]

An easy way to tell if your Chrysler 8.25 has factory limited slip is to Jack up the rear of the vehicle and turn one rear wheel by hand and if the other rear wheel turns with It in the same direction then you likely have a lsd. However if when you turn one of the rear wheels and the other rear wheel turns in the opposite direction then you likely have an open diff or a non working limited slip.

[Lost_Wrench]

Feels like it shifts normally but I guess I'll have to dive in deeper to see if anything is worn or improperly functioning. Thanks for the info everyone, I'll have to jack her up and see if it's a limited slip too.

[Wayne Sihler]

The terms Full Time and Part time are misleading. Both provide power to both axles.In Part Time the axles are locked together NO spillage between the two.
In the Full Time mode there is slippage in the transfer case, this releaves the stress in the drivetrain when the tires are on different types of surfaces.

[Jason77]

For what it’s worth, I’ve had two 231s, both in the same Jeep since I did a SYE on a donor and swapped it in, and a 242 on another. Both of the 231s shifted smoothly between modes in place. As long as I could get the shifter to move the light on the dash would change and they would be in that mode. The 242 in my ‘91 is more finicky. I can move the handle and the light will change but it won’t change modes until I move forward or reverse a bunch of feet. Even then sometimes I have to also work it through the modes while moving until I get it where I want. I got the 242 recently and it took me a little while to figure out that my shift technique had to be different.


Sent from my iPhone using Tapatalk

[Jason77]

Originally Posted by Jason77

For what it’s worth, I’ve had two 231s, both in the same Jeep since I did a SYE on a donor and swapped it in, and a 242 on another. Both of the 231s shifted smoothly between modes in place. As long as I could get the shifter to move the light on the dash would change and they would be in that mode. The 242 in my ‘91 is more finicky. I can move the handle and the light will change but it won’t change modes until I move forward or reverse a bunch of feet. Even then sometimes I have to also work it through the modes while moving until I get it where I want. I got the 242 recently and it took me a little while to figure out that my shift technique had to be different.


Sent from my iPhone using Tapatalk

Strike the part about the light changing, I can move the handle but the light on mine doesn’t always indicate what mode it’s actually in as far as I can tell. I might be miss remembering that part. The part about having to drive forward or back to get it to shift modes however is accurate.


Sent from my iPhone using Tapatalk

[Tim_MN]

The dashboard light indicates where the t-case ought to be, but not always where it actually is.

[Lost_Wrench]

Thanks everyone. Was messing with it today and I've come to the conclusion that no matter what I do, Part Time simply isn't working, regardless of the indicator lights. Full time is working great still. I was trying to get it to lose traction on the snowpacked roads today while running errands and it's very hard to do in Full Time. Its also shifting from 2wd to Full Time flawlessly. Just NO Part Time in either 4hi or 4lo, yet low still goes into low range but with only back wheels spinning. I plan on taking a closer look in the garage soon.

[Tim_MN]

Is the t-case shift mechanism properly adjusted ?

[Lost_Wrench]

It definitely feels normal when shifting. I will have to get under and take a closer look to be sure though.