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Author Topic: NP 242  (Read 1099 times)

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Offline Justink

  • Budget Lift
  • Posts: 278
  • '89 comanche 5'' lift, 33's
NP 242
« on: November 29, 2009, 04:23:55 PM »
On a NP 242 whats the difference between 4 hi full time and 4 high part time?
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'89 Comanche 5'' 33's, dana 44 playtoy
'91 cherokee 4.5'' 31's DD
'88 Nissan 300zx just for fun
If it seems like a good idea at the time it probably isn't!

Offline cLAY

  • Talks waaay too much!
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Re: NP 242
« Reply #1 on: November 29, 2009, 08:53:55 PM »
Full high means you can drive it in that position all of the time, its like an AWD setting, safe to drive on dry pavement with.
Part time means for off road or really slippery conditions only.

Green setting--> on road
Orange settings-->off road
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Offline Justink

  • Budget Lift
  • Posts: 278
  • '89 comanche 5'' lift, 33's
Re: NP 242
« Reply #2 on: November 29, 2009, 09:12:34 PM »
thats what i understood from the manuel.  Does the "off road" one lock up more tires or something?  Or does the "on road " on act as a sort of quadreatec system.  I tested them both today on loose ground and found that the only difference was i could lock up both tires in the part time
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'89 Comanche 5'' 33's, dana 44 playtoy
'91 cherokee 4.5'' 31's DD
'88 Nissan 300zx just for fun
If it seems like a good idea at the time it probably isn't!

Toy Jeep

  • Guest
Re: NP 242
« Reply #3 on: November 30, 2009, 08:32:49 AM »
Quote from: Justink on November 29, 2009, 04:23:55 PM
On a NP 242 whats the difference between 4 hi full time and 4 high part time?

In full time you have an open center diff. in part time hi you lock the center diff.
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Offline Justink

  • Budget Lift
  • Posts: 278
  • '89 comanche 5'' lift, 33's
Re: NP 242
« Reply #4 on: November 30, 2009, 10:33:34 PM »
So does that mean the front diff is different from one with a different t-case? And if its that much better why didnt jeep us that t-case in all models?
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'89 Comanche 5'' 33's, dana 44 playtoy
'91 cherokee 4.5'' 31's DD
'88 Nissan 300zx just for fun
If it seems like a good idea at the time it probably isn't!

Offline S-FLY

  • Budget Lift
  • Posts: 203
  • '94 XJ
Re: NP 242
« Reply #5 on: November 30, 2009, 11:11:55 PM »
The NP242 uses a viscous coupling that the NP231 didn't have. 

4wd part time means that you can only use it "part of the time".  It locks the front and rear drive shafts together.

Basically when you use 4hi or 4lo part time, if you turn the steering wheel on dry pavement, you'll destroy the front differential and or the transfer case because the inner wheel while turning will move at the same speed as the outer wheel causing it to bind.  If there's enough traction between that tire and the road, you'll break something.

4wd full time on the NP242 sends most of the power to the rear wheels but can send some of the power to the front wheels.  The front and rear drive shafts are not locked together, which allow you to run it on dry pavement because the transfer case allows the front wheels to move at a different speed than the rear wheels.
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Offline cLAY

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Re: NP 242
« Reply #6 on: December 01, 2009, 05:30:51 PM »
Actually there is no viscous coupling in the 24, its just like an open diff.  Only t-cases that end in a "9" like the NP249 found in the Grand Cherokees with Quadra-Trac have a viscous coupler. Here is an interesting read, scroll down to find the t-case info:

http://en.wikipedia.org/wiki/AMC_and_Jeep_transmissions

Why don't they put it in all Jeeps? Same reason why you don't get power windows and locks in all vehicles, cost.

Difference in front axles? The early XJs with the 242 got a front diff without the vacu-disconnect system and some of them also had CV axle shafts instead of u-joints. Later years they did away with the vacu-disconnect on all front axles.
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'93 ZJ, 5.2L, lifted/locked/36s..<gone>
'98 5.9er 4.10s,locked,LA,WJ knuckles

Offline S-FLY

  • Budget Lift
  • Posts: 203
  • '94 XJ
Re: NP 242
« Reply #7 on: December 01, 2009, 06:02:29 PM »
Ahh, you're right, my mistake.  Also explains why the 242 doesn't wear out like a viscous.
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ve1sly
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