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I had a transfer case that was super low on oil and I did not notice until I heard the high pitched squeal noise. Ended up changing out the fluid and the squealing is still there. Figured I'd have to change the transfer case.

It's a 1991 4cyl 5spd yj 1991. My question is which transfer case do I have? I assumed it's a np231...but even at that I'm not sure if a xj np231 would work. I found a rebuilt cj np231 with wide chain and sye, and I could install a used 6 planetary gear into it. But would this just bolt in or would I need a different yoke or driveshaft. I'm learning but I love the jeep community.

I've added pictures for attention! Haha any and all help is appreciated


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One thing you need to be aware of is the input shaft splines. There are 21 spline input shafts and there are 23 spline. My guess is since you are running a 4 cyl and ax5 that you have the 21 spline t-case. Some CJ t-cases I believe drop on the passenger side for the front shaft. You will need a drivers side drop. I cannot speak to how XJ parts fit into YJ's. Hope this helps.
 

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I found a rebuilt cj np231 with wide chain and sye

CJ's never had a NP231 and there are different spline counts and lengths on the input shaft depending the jeep it came in.

Was there a lot of metal in the transfer case oil when you drained it? It could be a bad bearing and you might be able to buy a rebuild kit and fix it if nothing is chewed up inside.
 

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Discussion Starter #4
CJ's never had a NP231 and there are different spline counts and lengths on the input shaft depending the jeep it came in.

Was there a lot of metal in the transfer case oil when you drained it? It could be a bad bearing and you might be able to buy a rebuild kit and fix it if nothing is chewed up inside.
CJ's never had a NP231 and there are different spline counts and lengths on the input shaft depending the jeep it came in.

Was there a lot of metal in the transfer case oil when you drained it? It could be a bad bearing and you might be able to buy a rebuild kit and fix it if nothing is chewed up inside.
My apologies. The np231 with wide chain and sye is from an xj I believe (2001 cherokee). I will messaged him and it's a 23 spline np231. So I'm guess this i

I actually had my mechanic change the fluid and he said it was extremely low, so since the fluid change didnt help the high pitched noise I figured I needed a new transfer case.

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Since you have a 4 cylinder you will need an NP 231J 21 spline T-case. Start looking on Car-Part.com--Used Auto Parts Market. I picked one up for my YJ from a junkyard for less than $300 shipped.


IIRC the XJ case has to clocked in order to fit a YJ there's something about the trans mount that's different also
 

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Discussion Starter #6
Found a used tcase with a chain problem for 60 bucks. Was thinking of taking this tcase, installing the 6 planetary gear, sye and wide chain....and then installing it in place of my tcase.

Any suggestions on which sye or wide chain kit? Seems like theres a bunch of sye that fit

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That squealing could be anything. I'd start over in your diagnosis of it, Don't assume anything. The Transfer case is pretty robust and uses a splash oiling system, so even a little lube will get the job done(but will get hotter quicker).
 

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Discussion Starter #8
Well I figured I wanted to beef up the tcase anyway since I was having problems.

I have a pre 1994 6 planetary gear. A backup tcase i found for 60 with a bad chain. Found a 1.25 chain out of a np231d. Now I just need the sprockets for the wide chain, and a sye.

Any suggestions on where to look for the sprockets. Having a hard time finding the specific ones for the pre 1994

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If you have some decently stocked junkyards around you can look at late 80's to early 90's Chevy S10 4x4 pickups (and the GMC versions). T/C will say 231C HD on them. It will have the wider chain and other parts to use. They're pretty abundant, so a little looking around should find you one.

These cases are actually super simple to work on. It would be super cheap to just replace bearings and see if that takes care of the problem, as suggested by another member. You should be able to tell if any of the bearings are roached on tear-down, so I'd recommend taking it apart and having a thorough look and then get what you really need.

If you're not gonna wheel the piss out of it the stock smaller chain is just fine, just needs to be checked for stretch while you're inside it.
 

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Discussion Starter #10
So this is the 6 planetary gear(early cut) I have and the driven sproket i have(also early cut).

I want to install these into my np231. Since my wrangler has a ax5, the output shaft is 21 spline. Would I need to purchase a 23 or 21 spline output shaft to work with this set up? Also I want a install a sye, anyone have any suggestions?


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No need to change the output shaft just to switch to the 6 gear planetary. You've already made sure the planetaries are the same cut, so you should be good to go.

Lots of SYE kits out there, the big name ones are all at least decent. You may have to remove the needle bearings for the SYE, depending on which one you choose...the directions should tell you ahead of time.
 

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Thanks for all the replies and assistance in this. My last question comes about driveshaft length. I measured from the transfer case back and took a picture. The pictured length looks to be about 25 or 25.5". The driveshaft are in sizes of .5". What do you guys think my driveshaft length is? Sorry for the dark pictures


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Thanks for all the replies and assistance in this. My last question comes about driveshaft length. I measured from the transfer case back and took a picture. The pictured length looks to be about 25 or 25.5". The driveshaft are in sizes of .5". What do you guys think my driveshaft length is? Sorry for the dark pictures


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You are measuring for a driveshaft and you don’t even have the (new) transfer case installed with the slip yoke eliminator incorporated into the equation?
 

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Discussion Starter #14
Well when ordering the SYE...I have the option of ordering a driveshaft with it. Was trying to figure out how exactly to do this
Basically I should install the new transfer case and then buy the driveshaft seperately?

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All the better driveshaft makers will want an exact measurement from yoke to yoke with the vehicle on the ground to get the perfect fit, so you don't "get shafted", pardon the pun. LOL.
 

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All the better driveshaft makers will want an exact measurement from yoke to yoke with the vehicle on the ground to get the perfect fit, so you don't "get shafted", pardon the pun. LOL.
Pardoning of puns promotes persistent punning.
Please pardon the prevalent Ps.

Good Luck, L.M.
 
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Drinking less water makes P less prevalent
 

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Drinking less water makes P less prevalent

Hmmm, I've heard that about beer too. But when I drank a lot of beer to see if it was true, I couldn't remember why I was drinking so much beer.

Good Luck, L.M.
 

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Discussion Starter #19
Woohoo as it has been awhile. I've finally got my transfer case in and got underneath with a tape measure. These are the pictures I've taken so far for measurements. To me I would say it's around 18inch from cap center to cap center. But the driveshafts come in lengths of .5" increases. So I'd hate to get a 17.5 or 18.5 and it be too large/small


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You need to measure in a straight line ie: if you're measuring from the top of the yoke on one end then you need to measure at the top of the yoke on the other end.
yoke.JPG

Who or where are buying this driveline? Anyone that makes custom shafts can cut the tube to the required length.

http://www.4xshaft.com/MeasuringGuide.pdf

This where I buy all my drivelines

http://www.4xshaft.com/
 
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