YJ t case swap

[thager35]

Have a quick question for the experienced jeepers here.. I have an 88 YJ automatic with a NP 231 t case that's starting to make some noise. I found a tcase from a friend of a friend he "said" came out of a XJ.. I went today and bought it for 50 bucks. The tag was all covered in grim and dirt I scratch the surface enough with my finger nail to see it said 231 on it. Upon closer inspection at home it say 231HD on it. I was wondering if this is still a direct swap and if it was a better/worse tcase that what I have? Any help would be appreciated!

additional info.. I cleaned tag alittle better and it actually says 231D-HD.. if that makes a difference?

 

[Bounty__Hunter]

That case is from a Dodge truck, YJ's and XJ's all say 231j.

Double check the input shaft but I'd bet it's different length and spline count. Not sure what else would be different. If it were me, I'd use the wide chain and planetary out of the 231HD to rebuild my 231j. But then again I've rebuilt hundreds of them.

 

[thager35]

That case is from a Dodge truck, YJ's and XJ's all say 231j.

Double check the input shaft but I'd bet it's different length and spline count. Not sure what else would be different. If it were me, I'd use the wide chain and planetary out of the 231HD to rebuild my 231j. But then again I've rebuilt hundreds of them.

thanks for the rely.. ive never rebuilt one but Im sure I could..

 

[thager35]

You think you could walk me thru the rebuild? Im pretty mechanically inclined... Ive just never tackled this. I tore apart the 231d just to take a look.. theyre pretty straight forward in there design.. I just don't know what has to be changed to make it work. thanks in advance! if its easier u can email me t_hager35@frontier.com I don't check these forums every day.. thanks again!

 

[jps4jeep]

I recommend IDing the problem first. a sound could be anything from a slacked out chain to a worn shifter fork. many parts from the dodge 231 will swap over to your jeep case. I believe all 21 spline 231 t cases, regardless of the make and model has the same input shaft length. 23 spline could be any of three lengths... but since you had an auto and assuming the xj was an auto, I assume it is 21 spline. To tear the case down, remove the front output assembly. Then move to the rear output and tear it down. Slip yoke, then speedo assembly eventually splitting the case. The main shaft, front shaft, and chain comes out as one unit from the front half of the case.


If the t case functions as it should, my money is on the chain being the issue, if the sound is only in 2wd or 4wd and not the other, shift fork... But this just a guess.

 

[thager35]

I recommend IDing the problem first. a sound could be anything from a slacked out chain to a worn shifter fork. many parts from the dodge 231 will swap over to your jeep case. I believe all 21 spline 231 t cases, regardless of the make and model has the same input shaft length. 23 spline could be any of three lengths... but since you had an auto and assuming the xj was an auto, I assume it is 21 spline. To tear the case down, remove the front output assembly. Then move to the rear output and tear it down. Slip yoke, then speedo assembly eventually splitting the case. The main shaft, front shaft, and chain comes out as one unit from the front half of the case.


If the t case functions as it should, my money is on the chain being the issue, if the sound is only in 2wd or 4wd and not the other, shift fork... But this just a guess.

Thanks for the reply... I was told it was from an XJ.. I assumed you read the earlier post where we figured out it was from a Dodge. The noise is constant... 4x4 2x4 slow fast turning... don't matter.. I have no idea if its chain noise..but it just sounds like a dry bearing..thats why im here.. for help.. what my question now is how to take the wider chain from the 231D-HD and rebuild my 231J.. I have a bearing kit here..I admit I haven't tore into it yet for diagnosis purposes. Another project in the garage in front of it. Thanks for the help! Im sure ill have some questions when I get started on it...

 

[Bounty__Hunter]

You swap the chain and both sprockets over to your 231, also swap in the planetary gearset if it has more gears than your current one. The donor case needs to be a similar year if swapping the planetary due to a change in gear cuts.

I'll help you as much as possible along the way, I've built hundreds of them.

 

[thager35]

You swap the chain and both sprockets over to your 231, also swap in the planetary gearset if it has more gears than your current one. The donor case needs to be a similar year if swapping the planetary due to a change in gear cuts.

I'll help you as much as possible along the way, I've built hundreds of them.

I really do appreciate it.. Im trying to get it in the garage.. I cant keep my kids cars out of there long enough.. hopefully very very soon.. I ordered a new set of 2.5 springs yesterday to replace my old wore out flat ones and have a new set of 31/1050/ mud tires setting in the corner itching to be put on.. Im gonna try to make it all happen next weekend. Thanks again bud.. I may have some questions when I tear into the transfer case project.. Ill try to get some pics up of the whole process..