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Np231j transfer case trouble shooting

6K views 10 replies 5 participants last post by  XJ93 
#1 ·
Ok you transfer case gurus, here is my symptoms, 1 transfer case runs fine no noise in all positions except 2 lh in 2 lh if fully engaged there is a slapping sound, if 2 h is just barely engaged there is no sound, here is what i know there was a stick stuck in the shifter mechanism, that would not allow the shifter to go all th way to 2h position, while changing the oil saturday i reached up and pulled it out, so when I got in it to drive it today i check the shifter and noticed it slid a little deeper in position this noise sounds like a missing tooth but if you just barely engage it runs smooth....4 h no noise
 
#6 ·
The slapping noise you are referring to is surely your chain slapping the top of the transfer case. This is a VERY common occurrence in our NP231's and is caused by the chain stretching out over time. Usually the slapping will only occur when running CAD axles when 4wd HI is engaged, if you still have a vacuum CAD or posi-lock CAD then your drive shaft shouldn't be spinning while driving in 2HI and thus the chain should not be spinning (or spinning very slowly if at all)...

Basically you need to make sure that your axle is fully disengaging, if engaged, you will be turning the chain in the transfer case at all times (which in it's self isn't bad, but is bad if your chain is stretched :D )...

What I don't understand is what you mean by "fully engaged" when referring to you moving the transfer case from 4HI to 2HI... Your transfercase is either engaged, or it isnt, there really isn't an inbetween when it comes to 2wd and 4wd HI... I recomend making sure your linkage is tight down there, the stick may have bent or loosened the linkage and could easily result in popping in and out of 4wd. Even then, popping in and out is usually pretty loud and nerve racking and from when i've heard mine pop in and out, not a sound that could be compared to subtle "slapping" haha.

Just some thoughts...
 
#7 ·
The shifter is a Novak conversion shifter I have been running it for years, if the rod has move and is short then do you think it would be possible to over shift the transfer case past 2h & into a bind... because that what it feels like... that maybe the stick could have cause it to thread in some or bent it short....or possibly I have ben running it only partially engaged and if so what damage could that have done that once fully engaged it would bang pretty good
 
#8 ·
Well to be honest, forcing the stick foward into "2HI" really shouldnt do too much damage... With the way the inside of the case is put together, forcing it further foward would simply force the main gear further onto the 2wd spline and further AWAY From 4wd... There isnt really any room in there to force the gear off the main shaft going towards the front of the case... Most damage to tcases in the area of engagement comes from engaging the tcase from neutral into 4lo or 4hi while moving... you get a seriously scary sound at that point lol... but even bumping into and out of 4wd hi while driving shouldn't hurt anything perminantly...

To be honest, it's really hard to tell not being there lol, try working with the linkage and if your 4wd starts to act up, then pop open the case and have a look... They are stupidly simple to open up and take appart... Wish I had more info for you lol but again, slapping sounds and noise usually comes from being engaged in 4wd or if you have the one piece axle shaft conversion up front which results in more moving parts in the tcase while driving.
 
#9 ·
The Novak Shifter Reverses I Shorten The Trow And It Stopped, The 2h Is Fully Engaged....ran 60 Miles No Problem
 
#10 ·
Okay,here's my dilemma: Transfer case shifts fine into 4 H,N,and 4L.However,on 2H,I am not able to turn the front drivehaft by hand more than 10 percent of a revolution.Also,drive front shaft does not turn if the jeep is rolled which appears to suggest that the problem is not in the vacuum disconnects.Occasionally,there will be a grinding noise in 2H and a quick shift to 4H and back to 2H will solve the problem.The TC is NP 231 J (YJ Reenegade).I distinctly remember of being able to turn front driveshaft freely by hand when in 2H.My confusion is that if the TC is not turning the driveshaft in 2H while driving normally (as it appears) how come its still connected to it in 2h?Please advise!
 
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