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Finally figured out why my N.P. 242 kept dis-engaging my front drive line!!

maddogs1965

NAXJA Forum User
Location
Truckee Ca,
So it took 2 times of dropping and splitting my T case in half, but i finally figured out why the front drive line kept dis engaging while the T case was in 4 LO.

The first time i split the T case in half, i just replaced the plastic bushings on the shift forks since they were broken and a couple completely gone from the end of the shift forks. Needles to say that did not help the situation one bit, the front drive line would still disengaged while in 4 LO.

So a couple of days ago i found a used 2000 N.V. 242 T case for 60 bucks that i am going to use for parts. So today i dropped my T case and split it in half again, and kept studying what made this thing tic.

So i figured out that the shift sleeve #33 slides into the Differential Assembly #36, and this is what in-gauges the 4 wheel drive, or basically your front drive line.

Before we go any further, here is the difference between a 242 and a 231 T case. The 242 has what they call a Differential Assembly inside the T case which the 231 does not have. The best way to explain the Differential Assembly is to compare it to a open rear end compared to a rear end with a locker in it. When you shift you lever inside the cab to 4WD HI part time, you are locking up the differential gears inside the T case solid like a locker would be in your rear end, so both the front and rear drive lines lock together as one solid unit, this is why it is recommended to only use full time on surfaces that are slippery, and can let the tires brake loose or spin while you are turning so you do not damage the gears inside of the differential assembly. When you shift your lever to 4WD HI Full Time, this makes the drive lines act like a open rear end in you truck, the tire with the least amount of leverage is always going to be the one to spin, or in this case, the drive line with the least amount of leverage is going to turn. This is why the 242 T cases turn corners so much better with the lever in the Full time position, it actually lets the front tires roll thru the corners instead of binding them them up like a normal T case does .

So now back too why the font drive line kept dis-engaging. When the shift sleeve #33 slides into the differential assembly #36, it actually has two positions, the first click or position on your T case selector is 4WD HI part time, which pushes the shift sleeve into the differential assembly grabbing the first set of gears to lock in the front drive line, and locking up the differential assembly solid and ties the drive lines together acting like a locker. The second position which would be 4WD HI Full Time pushes the shift sleeve further into the differential assembly, and grabs a second set of gears, which unlocks the differential assembly from the locked to the unlocked position, which lets the drive lines act like a open rear end, and slip in-dependability.
So when i was shifting all the way back into 4LO, there was just enough play on the shift rail #5, that it would let the shift sleeve #33 back out just enough so it was just in-between part time and full time causing my front drive line to free spool or dis-engage. There is maybe a 1/8Th of a inch in-between the Part Time Lock and the Full Time Lock gears, so there is really no room for the movement or wore out shift forks or the shift rail. I'm pretty sure the springs #8 & #11 on the shift rail that hold tension on the shift forks were also wore out and causing most of the problems, and letting the Shift Sleeve back out of the Differential assembly just enough to dis-engage the front drive line.

So after i figured out what was causing the front drive line to dis-engage, i split the 2000 N.V. 242 T case i just bought in half, and removed the whole shift rail assembly, both shift forks, and bushing #12 that goes into the back of the case that holds the shift rail in place, and installed it all back into my 242 case.

As i was re-installing the back half of my case back together, i could tell instantly that the new shift fork springs were allot tighter than what i just removed, i actually had to put pressure with my hand on the back of the case to be able to align it, and bolt it together, were as when i split the T case in half the first time, the back half of the case just fell on flush with no pressure needed.

So i took the Cherokee out to Prosser Dam Reservoir tonight, the lake is at it lowest to allow for spring time run off, so there are some pretty steep, rocky and loose sandy hills to climb, and no matter what i did even with the ARB locked in for the most amount of stress i could put on the front drive line in 4 LO, it never once dis-engaged Problem solved.... I hope this thread helps somebody else with the similar problems...

tcaes006.jpg
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Back in OEM.

Pic is ok as it comes with every SYE that is available on the market.
 
^ not true

please show me a SYE kit for an NP242 that also has an exploded view of that case

(not a Hack and tap)

ha! good point. I am thinking 231.
 
Good explanation of the 242's full-time option. Seems though, that you didn't know the full-time option worked with an "open diff" in the t-case, but I'm glad you know now. I wish more people understood the difference between full-time and part-time, so they quit using their part-time selection on dry pavement, and also quit using their full-time selection in mud/snow and complaining why only one rear or one front wheel was spinning! LOL

One other thing...and this is picky, I admint..but "in-gauges" should really be engages....sorry, I couldn't help it!
 
Thanks for your post! I'm glad you finally got it working, and I think your experience will help me get mine working again, even though I have a slightly different problem. I also have an NP242, but my problem is that when using 4FT, after just a short while it will disengage both driveshafts and feel like it's in neutral, but with a lot of extra noise (sort of a rough "whirring" that corresponds w/ engine speed).

I've searched a whole lot on this issue, but most responses suggested a linkage problem, which it is definitely not, as it still occurs while the linkage is disconnected and I've selected 4FT under the Jeep. I've lived with this problem for over 2 years, because all of the other positions work fine. And while I've found that having 4FT is obviously not necessary, it is the reason I purchased this box in the first place. Other suggestions I've found were a worn chain and to replace it w/ a 231. I replaced the chain several years ago because it was slipping and I'm not going to replace it w/ a 231 because I purchased it used to replace a 231. The case came with a SYE and driveshaft, so I'd definitely prefer not to buy another.

Your post makes me think my problem is somewhere between the forks, bushings, rails or shift sleeve. I'd been considering a rebuild kit for a long time, but perhaps I'll need additional parts. I believe a rebuild kit comes w/ the inserts for the shift forks, but the rest of it is all bearings and seals. It may be good insurance for my to buy the bushings and springs associated w/ the shifting mechanism as well. maddogs, did your shift rails and forks look overworn (as compared to the donor case), or would you say the spring replacement is what kept everything tight enough for the case to function well again? Did your shift sleeve show wear from the partial engagement?

This vehicle is my DD now that I've sold my car, otherwise I'd take it apart and have a look for myself.
 
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