NP242 torque split, center differential..

I recently bought an NP242 and was wondering how the torque split works exactly.

From my research, it appears that when both (front and rear) ends have equal traction, 60% of the power goes to the rear, and 40% of the power goes to the front.

OK, so the front AND rear aren't locked to the input shaft, right? IE the rear isn't spinning all the time, with the front has a differential. That leads me to my next question;

people say that when a single end loses traction, (IE you diconnect the front drive shaft) all the power will go to that end. 100/0 split to the end with the least traction. Wouldn't this make full time 4x4 useless? If your back tires are on ice, as is a lot of time in Canada, and your front tires are on pavement, won't your back tires just sit and spin and you'll go nowhere? How does this lead to more traction on these conditions?

On a Subaru, the computer detects this and will send more torque to the front wheels, however, this NP242 isn't that smart and so isn't it practically 2wd? But I've heard it gives a lot greater traction on wet, snow, and ice conditions. Am I really misunderstanding something?

mattbred said:

On a Subaru, the computer detects this and will send more torque to the front wheels, I really misunderstanding something?

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yup,on a sube you either have a center viscous coupling (MT-5+6speed, will allow slight differential action) or a center diff clutch pack with a hydraulic actuator(4spauto-od) ,50/50 split, hit a cross ditch one front wheel one back wheel will spin. much like part time on a 242

Its true that if you have no front shaft on, it will just spin the yoke. I found that out last weekend when i replaced my 242 for a newer one. If you have a situation like the one you described, you should still be able to get enough resistance to get both axle going. But if you can't, wouldnt it just make sense to just put it into part-time? That will solve the issue you speak of. And I figure thats why New Venture made them like that. Also, its a 58rear/42front split.

XTurboJ said:

Its true that if you have no front shaft on, it will just spin the yoke. I found that out last weekend when i replaced my 242 for a newer one. If you have a situation like the one you described, you should still be able to get enough resistance to get both axle going. But if you can't, wouldnt it just make sense to just put it into part-time? That will solve the issue you speak of. And I figure thats why New Venture made them like that. Also, its a 58rear/42front split.

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Or just tap the brakes while giving it gas.

I can't say how the NP242 works exactly.

But, I can say that anyone who says that in full-time, when a single end loses traction, all the power will go to that end don't know what they are talking about.

I'm running a NP242 with 4.56 gears and a Detroit locker. In full-time, on a rain slick road, I can make a hard right hand turn under full throttle, and break the rear end loose, the front end continues pulling through the turn.

I suppose if you removed the rear shaft and eliminated all bias, the front yoke would spin but, just put it into part-time and go. . .

I have a 242 in my XJ and it will give power to the wheel or wheels with the least amount of traction, you really need to be carefull and learn when and when not to use it. There have been times where I am in fulltime 4x4 where I pull out onto a wet road under full throttle and just one tire will spin, it could be the front or it could be in the rear. There is no 50/50 torque split in it its just like the open diffrential in your axle, power goes to the wheels of least traction. Think of your rear axle with a open diffrential, if you go around a sharp corner and floor it the inside tire will spin like crazy because it has the least amount of traction. The 242 in fulltime mode will do the same thing except now it has 2 axles and 4 tires to choose from. Now if traction between all tires is equal the Fulltime mode works good. I pretty much only use it when I need to pull out into traffic fast without just sitting there spinning my tires. On dry pavement it works awesome, on wet pavement I have found that sometimes it will just spin one tire.

As an owner of an XJ with a 242, I just had to comment. Previous posts are correct...in the full time mode the transfer case acts like an open diff. It sends power to all four wheels, but exhibits the characteristics of an open differential between the front and rear drive shafts. It is possible (likely if you use enough skinny pedal) to have only the front or rear getting torque.

The advantage of the 242 is only realized with a level-headed driver...don't mash the skinny pedal when the roads are slick! A gentle touch on the gas will deliver performance not available with a "part time" mode, and will allow drive shaft differentiation when turning. See, with a part time mode, turning a corner means one wheel (usually the outside front) must skid...slide...whatever. That skidding means it looses traction. The 242 allows all wheels to power without skidding, if you use the skinny pedal correctly.

On an icy, snowy, or otherwise slick street, you COULD engage lockers on both axle diffs, and put the transfer case in "part time", and spin all four! But what use is that...a spinning tire has no traction...no steering..and little control!

The advantage of the 242 is that it offers both modes. I love the fact that on slick (snow, rain) roads, I can run "full time" without worrying about the occasional dry patches or corners putting extra strain on drive train components. Just drive like a reasonable person...enjoy the advantages. It's not computer controlled...just takes some driver ability and knowledge to make it work to it's maximum.

Just my two-cents.

Okay, so as long as every wheel has SOME traction, the Jeep will have better traction than 2-high.

What if one were to run limited slips in the front and rear axles, along with fulltime 4x4?

Flyfisher said:

As an owner of an XJ with a 242, I just had to comment. Previous posts are correct...in the full time mode the transfer case acts like an open diff. It sends power to all four wheels, but exhibits the characteristics of an open differential between the front and rear drive shafts. It is possible (likely if you use enough skinny pedal) to have only the front or rear getting torque.

The advantage of the 242 is only realized with a level-headed driver...don't mash the skinny pedal when the roads are slick! A gentle touch on the gas will deliver performance not available with a "part time" mode, and will allow drive shaft differentiation when turning. See, with a part time mode, turning a corner means one wheel (usually the outside front) must skid...slide...whatever. That skidding means it looses traction. The 242 allows all wheels to power without skidding, if you use the skinny pedal correctly.

On an icy, snowy, or otherwise slick street, you COULD engage lockers on both axle diffs, and put the transfer case in "part time", and spin all four! But what use is that...a spinning tire has no traction...no steering..and little control!

The advantage of the 242 is that it offers both modes. I love the fact that on slick (snow, rain) roads, I can run "full time" without worrying about the occasional dry patches or corners putting extra strain on drive train components. Just drive like a reasonable person...enjoy the advantages. It's not computer controlled...just takes some driver ability and knowledge to make it work to it's maximum.

Just my two-cents.

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Agreed x2. I LOVE the 242.

mattbred said:

Okay, so as long as every wheel has SOME traction, the Jeep will have better traction than 2-high.

What if one were to run limited slips in the front and rear axles, along with fulltime 4x4?

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In the worst case scenario, you could spin both tires on one end of the car and not go anywhere if you have selected full-time 4WD on the transfer case. If you want to be able to spin all the tires, you'll need lockers and you'll need to select part-time 4WD on the transfer case. You may not want to drive on ice or snow with lockers that can be turned off. The car will not want to go where you want it to go on ice when you're locked.

PaulJ said:

In the worst case scenario, you could spin both tires on one end of the car and not go anywhere if you have selected full-time 4WD on the transfer case. If you want to be able to spin all the tires, you'll need lockers and you'll need to select part-time 4WD on the transfer case. You may not want to drive on ice or snow with lockers that can be turned off. The car will not want to go where you want it to go on ice when you're locked.

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The issue of having limited slip both front and rear is problematic only on very slick roads (ice and snow). If the LS's work, they will tend to make either the front or the rear, or both slide/skip somewhat. Remember, when tires slide they have NO traction. I disagree with PaulJ...selectable lockers are exactly what you want with the 242...the ability to turn them on and off is exactly the kind of control you want with a full-time system...the ability to run full-time without either axle locked.

Personally, I'm fitting a Ford 8.8 to the rear of my XJ with an Ected limited slip/locker, and leaving the front with an e-locker. That way, the limited slip is only in the rear...providing extra traction in ice/snow without inhibiting steering...leaving me the ability to run in "full-time" mode on the icy/snowy highway. With my selection, I have the ability to run locked at either/both ends for rocks/mud/what have you.

Again, just my 2-cents worth.

I realize I am resurrecting an old thread but being the owner of an XJ with the NP242 and being well into my 14th Midwest winter driving it, I wanted to add my thoughts.


Yes, it's true that when in Full-time mode the NP242 acts as a center open differential, meaning that if either end of the car has absolutely no traction, that's where the torque is going to go. BUT: in reality that would be a very rare occurrence and as previously written, a quick flick of the lever to Part-time will lock it up, or simply applying some brake with the left foot on the brake pedal while giving it gas will spread the torque to the front and rear.


I can tell you that I LOVE keeping it in the Full-time mode in wet or snowy weather. One can accelerate strongly from stoplights, stop signs and around corners without having the rear tires break loose and/or flaring out when cornering. I know it's a little bit sociopathic of me, but when I approach a stop sign or red light after being stuck behind the typical slow driver creeping along because they can't be bothered to buy proper winter tires and usually have just FWD or even RWD, I LOVE pulling up on their right and when the light changes, flooring or almost flooring it and pulling away as if I am on a dry surface. The best times of this are when they actually try to keep me from passing them. They stand no chance. I didn't even know about the NP242 when I bought my Jeep - I was lucky to end up with a Cherokee with it. And the optional and rare ABS brakes, too. Equipped with the NP242 and ABS, it's the perfect winter vehicle for Chicago.

Best wishes,


John

Flyfisher said:

As an owner of an XJ with a 242, I just had to comment. Previous posts are correct...in the full time mode the transfer case acts like an open diff. It sends power to all four wheels, but exhibits the characteristics of an open differential between the front and rear drive shafts. It is possible (likely if you use enough skinny pedal) to have only the front or rear getting torque.

The advantage of the 242 is only realized with a level-headed driver...don't mash the skinny pedal when the roads are slick! A gentle touch on the gas will deliver performance not available with a "part time" mode, and will allow drive shaft differentiation when turning. See, with a part time mode, turning a corner means one wheel (usually the outside front) must skid...slide...whatever. That skidding means it looses traction. The 242 allows all wheels to power without skidding, if you use the skinny pedal correctly.

On an icy, snowy, or otherwise slick street, you COULD engage lockers on both axle diffs, and put the transfer case in "part time", and spin all four! But what use is that...a spinning tire has no traction...no steering..and little control!

The advantage of the 242 is that it offers both modes. I love the fact that on slick (snow, rain) roads, I can run "full time" without worrying about the occasional dry patches or corners putting extra strain on drive train components. Just drive like a reasonable person...enjoy the advantages. It's not computer controlled...just takes some driver ability and knowledge to make it work to it's maximum.

Just my two-cents.

Click to expand...

Agreed x 10

mdtobe said:

...I can tell you that I LOVE keeping it in the Full-time mode in wet or snowy weather. One can accelerate strongly from stoplights, stop signs and around corners without having the rear tires break loose and/or flaring out when cornering. I know it's a little bit sociopathic of me, but when I approach a stop sign or red light after being stuck behind the typical slow driver creeping along because they can't be bothered to buy proper winter tires and usually have just FWD or even RWD, I LOVE pulling up on their right and when the light changes, flooring or almost flooring it and pulling away as if I am on a dry surface. The best times of this are when they actually try to keep me from passing them. They stand no chance. I didn't even know about the NP242 when I bought my Jeep - I was lucky to end up with a Cherokee with it. And the optional and rare ABS brakes, too. Equipped with the NP242 and ABS, it's the perfect winter vehicle for Chicago.

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You sound like a real jerk behind the wheel.

smccollamjr said:

You sound like a real jerk behind the wheel.

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You sounds like the typical driver that likes to drive 15 under in the fast lane and police the roads when you have no right to do so. Stay in the slow lane, grandpa.

ditchdrift said:

You sounds like the typical driver that likes to drive 15 under in the fast lane and police the roads when you have no right to do so. Stay in the slow lane, grandpa.

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I read that comment, then your username and had to laugh. I’ll stop hijacking this thread now.

I'm sorry I have to agree. Some people can drive in snow,some can't. I have a few 4wd-AWD vehicles usually equipped with snow tire's. I have prepped and paid for that ability. Why should the lesser equipped try and police the road?
I live in Colorado and regularly see the subarus in the ditch and lesser vehicle's in the left lane.
I travel to the mountains fairly often. I love seeing the van shuttle come flying last,then on the next corner in the ditch.