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Unread 09-18-2010, 08:09 PM   #1
07lane40
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Np231 hd

Hi all,

I am in the process of getting an np231D HD into my jeep. however i realized i need to swap my rear output shaft from my 231J and tailcone for this to work because the NP231D's tail shaft and tail cone are much too long and also too thick. Do i need to swap the tailshaft housing to the 231J too inorder for this to work?

I have a stuck bolt on the 231D and cannot get the tailshaft housing to come off. Can i just split the case and swap the shafts? The case would only separate approximately half an inch and i cant seem to get it any further - i dont want to damage anything, can i just put some muscle into it? I cannot seem to find a write up on how to do the tailshaft swap from the 231J to the 231D so i can get the HD unit into the jeep. can you guys help me out? this is my DD so i cant have it down for too long

Thanks!!

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Unread 09-18-2010, 09:00 PM   #2
moonshinefuel
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To split the case completely requires taking off the part of the t-case that the speedometer attaches into, otherwise it will hold it at about a half inch. To take that part off the t-case requires heavy duty snap ring pliers.
What year is the "HD" transfer case, and what year is yours?
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Unread 09-18-2010, 09:06 PM   #3
07lane40
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my tcase is from a 93 and i believe the HD is a 95. they are cosmetically identical just different tailshaft dimensions and cone structures.. according to other stuff i have seen they are both "early" style t/c's.
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Unread 09-18-2010, 09:18 PM   #4
moonshinefuel
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Yes, 1995 was about the time where there were those changes made, and differences, input shafts from the t-case fitment into the transmission were designed longer. I think maybe you are going to get into a situation where there may be some fundemental differences inside each t-case.
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Unread 09-18-2010, 09:42 PM   #5
moonshinefuel
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I think the question is going to be, how much of the internals of your current t-case are you going to have to swap into the "HD" case to make it work? I mean it might work, just don't know. There are different angle gear cuts on planetary gear assemblies on some. Just can't say for sure exactly what you are dealing with.
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Unread 09-19-2010, 07:32 AM   #6
07lane40
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well... if worst comes to worst ill jjust throw my 231j back in deal with 2wd then do an sye on the 231D and then throw it in. :-/

i am gonna try and break them down further today... maybe i can just swap the 231d chain and chain gears over to my 231j.... cause my chain is what's bad.

I'd just like to have the extra security of the 231d once i go taller and bigger tires.

thanks for the help
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Unread 09-19-2010, 07:44 AM   #7
07lane40
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i dont know if anyone has posted this up here but i just found an np231 service manual looks helpful to me and may be to someone else - so here is the link

http://www.pirate4x4.com/tech/billav...Case_NP231.pdf
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Unread 09-19-2010, 04:35 PM   #8
07lane40
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some info for all. i found out today that...

the Dodge and Jeep NP231 input/output shafts swap out pretty easy.
Not all dodge np231's have 6 planetary gears. my 231d only had 3. - the only thing HD about it was the thick chain.
the problem with my tcase was that it had been burned out from the p/o driving without oil in it. - specifically the shift fork pads.
Check the magnet regularly - there was all kinds of shavings on mine.
lastly i now know how to completely tear down and rebuild np231s and ive never touched a transfer case before.

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Unread 09-19-2010, 09:04 PM   #9
moonshinefuel
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Good info. So have you figured out how you are going to put it all into one case? Are you going to use the D case, or the J case?
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Unread 09-20-2010, 06:57 AM   #10
07lane40
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I used the J case because they are the same structure and it meant less time converting the output shaft. The planetary gearset was the same (both 3) - which i was very disappointed in - so i basically just converted to the wider chain along with larger shift fork and shift collar from the D case.

So if nothing else i got the HD chain (which runs as a kit for 425) for 150. and spare case halves and spare chain/gearsets.

the hardest part about everything was the snap rings. even with snap ring pliers they were a ***** and took forever.

all i have left to do is get a new tailcone (mine broke because of a blown u joint - i think) or try and seal mine up and put that on, bolt the case into the jeep, fill'er up with oil and go do some wheelin!
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Unread 09-20-2010, 07:03 AM   #11
07lane40
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so i guess that brings me to another question...

one of the bolt holes on my tail cone snapped off which caused it to leak out some oil. can i just seal up the break with rtv and be okay? its a clean break and still has some structural strength (it is angles about 45* to the flat surface.

i guess my real question is does the tail cone have any structural purpose other than to hold the rear seal?

if not i plan on rotating the tail cone till the break is on top and just sealing it up good with rtv or maybe JB weld?

is this an okay idea?
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Unread 09-20-2010, 01:55 PM   #12
murilstone
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i could mail you a tail cone...all you have to do is pay shipping. i live in Independence, MO ( 64050 ) if you figure out the shipping and it is worth it PM me and we can set it up.
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