having issues with a N.P. 242 T case!!

So i have a 91 Cherokee with from what i can figure out is N.P. 242 T case. Part # R2098899.

So yesterday since there is no such thing as snow in Truckee this winter, a couple of buddy's and myself decided to drop in to Fordyce, and drop down to the first river crossing.

So i dropped the air pressure in my tires and locked in the hubs. (She has a Dana 44 H.P. out of a 76 Ford F-150 shopped and narrowed with Dutchman Chromo axles & CTM's) So I'm cruising down the trail in 2 wheel drive until i hit some ice and snow in 2 wheel drive, throw the T case into 4 low, the T case drops into 4 LO, but no 4 wheel drive. I thought maybe one of the Warn hubs did not lock in fully, but upon further inspection and process of illumination, we figured out the front drive line is not in-gauged in the T case and pulling the front end. We could unlock the hubs, and grab the front drive line, and turn it while the T case was in 4 LO. You can feel its trying to in gauge the drive line, but not fully locking in, some times it would grab, and some times it would not. So we thought the linkage on the T case was out of adjustment, so we messed with it on the trial to no avail.

So i get the Cherokee home and in the garage this morning, and remove the linkage going to the T case, and manually with my hand push the lever on the T case in 4 Lo....same thing, some times it locks in the front drive line, but dis-engages.

So i did some research on this T case, and figure out it has a part time 4 wheel Hi and a Full time 4 Hi. Basically this means the T case has a centrifugal clutch set up in it. While in part time 4 wheel drive, the centrifugal is supposed to send more power to the wheels that are spinning. While in full time 4 wheel, it is supposed to lock the front and rear together like a normal transfer case does.

So i re-install the T case linkage and start playing with the shifter. If i shift from 2 wheel drive to part time 4 wheel drive, everything is just fine, but if i go from part time to full time 4 wheel drive, and go from drive to neutral in the tranny (its a automatic) the T case goes into neutral and i hear a slight werring sound coming from the T case, but if i push it back into part time 4 wheel, the gears slam a little bit, but the T case is back in gear and will move the Jeep again....I have done this procedure at-least 10 times, and it has the same effect wether the tranny is in gear or not, the T case will go into neutral or never never land as soon as you put the T case into 4 wheel full time . 4 LO will in-gauge in the T case and stay in-gauged, but the drive line will not full lock in enough to pull the tires, and even if it does, you can hear the drive line dis-engauge as soon as you get any pre -load off the drive line.

Unfortantley this is my daily driver, so if it ever does snow i will need my 4 wheel drive to be functioning correctley to get me to work.

:helpme: so has anybody else had this problem? I have no problem dropping the T case and splitting it in half and fixing what ever is wrong, but I'm not sure what I am really looking for once i do split it in half, im thinking a shift fork or a detent ball or spring took a crap.

This Transfer case was supposedly exchanged or re built 3 to 4 years ago bye the P.O. The original tag on the T case is from Mopar, and not Jeep .

Thanks for any help

Rick

here is a pic of some spring wheeling in the Con when we actually had some snow a couple of years back.

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Somebody has to have a idea on what the heck is going on with this T case, a little :helpme: PLEASE!!!

So it used to go into all the ranges before (4l,4h FT, 4h PT, 2H ). As long as you know the linkage is adjusted right, it looks like your shift fork or mode fork are not doing there job.

The forks have plastic guides on them and when they wear out the fork binds up and will not have full engagement.

My 89 XJ was making loud popping noises on me in 2 and 4 wheel, put a used T Case to get on the road. Pulled old NP 242 case apart and the only thing I saw that was bad were those plastic fork guides. T case had 4000,000 mi. on it so I was surprised. Good luck.

OK...if you have the 242, your shift gate (in the cab) has a position for 4-full time, and 4-part time. You seem confused as to the meaning of "full time" and "part time". In full time, a center (transfer case) differential is engaged, meaning you can actually only have power to one front, or one rear wheel. In "part time", the center (transfer case) is locked, meaning the front and rear drive shafts are locked...power to at least one front, and one rear wheel.

That's a nice looking outfit, by the way...hope you're not the dog driving. I just think you are confused about part time and full time. Full time is for use on any surface, at any time. It will differentiate between the front and rear drivelines. Part time is for use part of the time..only on slippery surfaces...and will lock the front and rear drive shafts together. If you use part time 4x on pavement, it will bind up...skip tires...and generally not be good for things. On the 242, in low range, it's in "part time"....front and read drive shafts locked together.

I cannot believe you have such a nice rig and don't know this. It's clearly explained in the owners manual, and on the driver's visor. Also, you should try to check your spelling...your terms are confusing at times.

my2monkeys said:

So it used to go into all the ranges before (4l,4h FT, 4h PT, 2H ). As long as you know the linkage is adjusted right, it looks like your shift fork or mode fork are not doing there job.

The forks have plastic guides on them and when they wear out the fork binds up and will not have full engagement.

My 89 XJ was making loud popping noises on me in 2 and 4 wheel, put a used T Case to get on the road. Pulled old NP 242 case apart and the only thing I saw that was bad were those plastic fork guides. T case had 4000,000 mi. on it so I was surprised. Good luck.

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Thanks for the reply back.....

The T case has worked fine for the last 3 years i have owned the Cherokee, this problem just popped up Saturday morning. I could not tell you if 4 hi part time ever worked or not, i just always thew the T case in to 4 wheel full time when i was driving on the road in the snow to get me to work, if I'm 4 wheeling, the T case is always in 4 lo so i don't cook the tranny I think the popping you would be referring to was the gears not completely meshing all the way, and then popping back out.

Rick

Flyfisher said:

That's a nice looking outfit, by the way...hope you're not the dog driving. I just think you are confused about part time and full time. Full time is for use on any surface, at any time. It will differentiate between the front and rear drivelines. Part time is for use part of the time..only on slippery surfaces...and will lock the front and rear drive shafts together. If you use part time 4x on pavement, it will bind up...skip tires...and generally not be good for things. On the 242, in low range, it's in "part time"....front and read drive shafts locked together.

I cannot believe you have such a nice rig and don't know this. It's clearly explained in the owners manual, and on the driver's visor. Also, you should try to check your spelling...your terms are confusing at times.

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First off, I never use the part time 4 wheel Hi in the T case, to be honest with ya, the centrifugal in the T case is just 1 more thing to go wrong as far as i am concerned. It still does not explain why the front drive line is not locking in in 4 LO and pulling the front tires, and it still does not explain why when the T case is in 4Hi full lock, the Jeep does not move like the T case is in neutral..... and the reason i don't know anything about these T cases is because this the first Jeep i have owned, I'm used to a real T Case like a Dana 205, or the T case that comes in this :shhh: all gears and no centrifugal B.S. It sounds like to me my shift forks have taken a poo poo on me in the 242....:gee:

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FULL-TIME is the differential. PART-TIME is full 4WD.

All the transfer case does is move power from the transmission to one or both driveshafts. In 2WD the rear driveshaft gets all the power. In PART-TIME 4WD (HI or LO), driveshafts are locked together. On the 242, there is an extra position for FULL-TIME 4WD that engages a differential, which passes the power to the driveshaft with the least resistance.

Part-time is meant to be used "part of the time" and should only be used when surface conditions allow the front and rear wheels to break contact and slip/spin (the driveshafts will force at least one wheel on each axle to spin at the same rate so if you are turning one of the wheels is going to have to slip/break free). Full-time is meant to be used "full time" and can be used on any surface, since only one of the driveshafts is getting any power. Dirt/gravel=PT, Ice/rain/pavement=FT

maddogs1965 said:

First off, I never use the part time 4 wheel Hi in the T case, to be honest with ya, the centrifugal in the T case is just 1 more thing to go wrong as far as i am concerned. It still does not explain why the front drive line is not locking in in 4 LO and pulling the front tires, and it still does not explain why when the T case is in 4Hi full lock, the Jeep does not move like the T case is in neutral..... and the reason i don't know anything about these T cases is because this the first Jeep i have owned, I'm used to a real T Case like a Dana 205, or the T case that comes in this :shhh: all gears and no centrifugal B.S. It sounds like to me my shift forks have taken a poo poo on me in the 242....:gee:

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A few things:

When you are offroad, you should be using the part time 4wd. When I first got my Jeep, I did the same thing because I thought it meant "4wheel drive will only work part of the time." (I was young, it was my first vehicle)
The NP242 is a real transfercase. Just because it is a chain and not gears does not make it a fake transfercase.
What centrifugal BS are you talking about? I don't know of any "centrifugal" in the t-case.

Your probably going to have to pull the T-case, that shouldn't be bad with being so high off the ground.

I got my used T-case down in Antelope at J & W Jeeps yard (near Sacto.).

It was pulled from the donor rig already. $350 no core charge.

They have a web site, I got a quote on line and when I went to get it the price was like $500 until I told him what they quoted me!

So get a quote first! Good luck

my2monkeys said:

Your probably going to have to pull the T-case, that shouldn't be bad with being so high off the ground.

I got my used T-case down in Antelope at J & W Jeeps yard (near Sacto.).

It was pulled from the donor rig already. $350 no core charge.

They have a web site, I got a quote on line and when I went to get it the price was like $500 until I told him what they quoted me!

So get a quote first! Good luck

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$350? :scared:

You can get them around here for $100-$150 all day long already pulled.

ehall said:

FULL-TIME is the differential. PART-TIME is full 4WD.

All the transfer case does is move power from the transmission to one or both driveshafts. In 2WD the rear driveshaft gets all the power. In PART-TIME 4WD (HI or LO), driveshafts are locked together. On the 242, there is an extra position for FULL-TIME 4WD that engages a differential, which passes the power to the driveshaft with the least resistance.

Part-time is meant to be used "part of the time" and should only be used when surface conditions allow the front and rear wheels to break contact and slip/spin (the driveshafts will force at least one wheel on each axle to spin at the same rate so if you are turning one of the wheels is going to have to slip/break free). Full-time is meant to be used "full time" and can be used on any surface, since only one of the driveshafts is getting any power. Dirt/gravel=PT, Ice/rain/pavement=FT

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I think that is about the best explanation i have read....

So the only time i use 4 wheel Hi is when I'm driving to work in the middle of a snow storm, and hard pack snow is on the road. So with that being said, with a Detroit Locker in the rear, would you recommend Part time since the wheels need to slip? I have always used the Full time lock position..

As far as playing around and 4 wheeling, I just throw it into 4 Lo since i want to crawl ......

So which T case do you think is stronger? the 242 or the 231? or are they same strength just minus the full lock and part time lock in the Hi position?


I'm also thinking about switching from the 242 i have to a 231, will this T case work in my 91? I'm not sure if the input spline count is the same. I am also thinking about removing the 242 for a newer Jeep Rubicon T case. Don't quote me on this, but i think the input spline count on the 242 is 28, and the spline count on the newer Jeep Rubicon T Case is 31?

Nope, the 91 should be a 23 spline input, as well as the rubicon's NV241OR.

Renix (84-90) are 21 spline,
HO (91-01) 23 spline.

Begster said:

Nope, the 91 should be a 23 spline input, as well as the rubicon's NV241OR.

Renix (84-90) are 21 spline,
HO (91-01) 23 spline.

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Thanks!!

the 242 and 231 are pretty much the same strength. any time you are on the street use full time. dont use part time on the street. even with your locker. it sounds like you need to rebuild or replace that 242. a rebuild is pretty easy and cheap. takes but a day or two with simple hand tools. i did it to mine about a year ago. i wanted the piece of mind knowing it was rebuilt versus getting a used unit

1990JEEPXJ said:

the 242 and 231 are pretty much the same strength. any time you are on the street use full time. dont use part time on the street. even with your locker. it sounds like you need to rebuild or replace that 242. a rebuild is pretty easy and cheap. takes but a day or two with simple hand tools. i did it to mine about a year ago. i wanted the piece of mind knowing it was rebuilt versus getting a used unit

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I plan on dropping the case this weekend and splitting it too see what is going on inside. I know it has already been re built once, it has the Mopar tag on it instead of the Jeep tag. It never made any kind of bad noises are gears popping in and out, so I'm hoping it has some thing to do with the shifter forks.

I will let you guys know what i find this weekend.

Rick

maddogs1965 said:

So the only time i use 4 wheel Hi is when I'm driving to work in the middle of a snow storm, and hard pack snow is on the road. So with that being said, with a Detroit Locker in the rear, would you recommend Part time since the wheels need to slip? I have always used the Full time lock position..

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You still have it wrong. Part time won't allow the drive shafts to move independently. Full time will, and its not "lock" either.

Talyn said:

You still have it wrong. Part time won't allow the drive shafts to move independently. Full time will, and its not "lock" either.

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As far as I"m concerned, if Part time is locked, then they should call it Full time, and when the tires spin, it should be called Part time :looney: Doesn't that make more sense :dunno: But i do understand the difference between Part Time and Full time now, it was a typing error.


So on a better note, i did figure out what was wrong with the front drive line not locking in when i put the T case in 4 Hi Part Time, and the Transfer case acting like it was in neutral and not moving the Jeep......basically not a darn thing.

On my way to work this morning i was wracking my brain on what could be going on with the T case. Then i remembered trying to install a set of lock/unlocking hubs on a friend's Full Time 4 wheel drive old school Chevy Blazer 20 years ago instead of the blanks that came on the front end from the factory with Hi & Hi Lock and Lo & Lo Lock in the T case. We figured out the hard way if the front hubs we installed were not in the locked position, the vehicle would not move.

The best way i can describe this is if you have a open rear end, and you brake a rear axle, even though you still have one good axle, the spider gears will not recognize this, and will just keep turning the broken axle. The axle with the least amount of resistance is going to be the one that spins. In another word's, you are dead in the water, and the vehicle will not move.

Well this is the same thing that is going on with my T case in the Cherokee in 4 wheel Full time, if i do not have the front hubs locked in, the T case will not sense equal pressure on both drive lines, so then the Cherokee would not move and act like the T case was in neutral.

When i got to work this morning, i locked in the hubs in, and threw the T case into Full Time 4 Hi, and walked wright up the pile of gravel in front of me. Got back out, and unlocked the hub's, threw the T case back into Full Time 4 Hi, and ZING, nothing happening just like the T case was in neutral.

So i am assuming this T case is just like my friends old school Chevy Blazer, no front drive line pressure sensed inside the T case to match the rear drive line , no go!!!!! Since this was a stock Jeep at one time with a Dana 30 front end, with no hubs, but a vacuum modulator to lock in the front axle, this is no problem, but with the hubs unlocked, SHE NO GO!!!

So know i am down to one problem, the front drive line not completely locking in while in 4 LO. I am assuming this is either related to the plastic bushings being gone on the 4 LO shift fork, or the shift fork is bent. I ordered the complete plastic bushing kit for both shifter forks from FWD.com lastnight but they are back ordered :smsoap:

I will let you guys know the out come of the 4 LO problem when i get the bushings in, and the T case split...

yes. shouldve specified. i have removed my front driveshaft and tried to move in full time before. didnt work. spins the front yoke since the open diff sends power to the side with less traction. in full time, the transfercase acts exactly the same as an open differential with the driveshafts being the same as the axle shafts.

maddogs1965 said:

As far as I"m concerned, if Part time is locked, then they should call it Full time, and when the tires spin, it should be called Part time :looney: Doesn't that make more sense :dunno:

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It's not really a question of which one is better so much as the semantics are really confusing and entirely different phrasing should have been chosen. That's true for 4WD and AWD too. Really we are talking about driveshafts, not wheels, not "part-time," etc. The auto-industry wasn't good with a lot of stuff in the 80s and 90s.

When i got to work this morning, i locked in the hubs in, and threw the T case into Full Time 4 Hi, and walked wright up the pile of gravel in front of me. Got back out, and unlocked the hub's, threw the T case back into Full Time 4 Hi, and ZING, nothing happening just like the T case was in neutral.

So i am assuming this T case is just like my friends old school Chevy Blazer, no front drive line pressure sensed inside the T case to match the rear drive line , no go!!!!!

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Pretty much. It's a real differential in the 242, so power is directed to the output that has the least resistance, and if you unlock the hubs then the front driveshaft will definitely have the least resistance. The transfer case model on your friends K5 was different, but it also had full-time.