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NP231 rebuild/upgrade recommendations

montanaman

NAXJA Forum User
Location
Western Montana
Time to rebuild my '91 NP231-J (with the long tailhousing).

I need recommendations for the following:

- Does my version have the 16mm or 24mm input bearing? I think it's the 24, but not sure.
- A good rebuild kit with high-quality Japanese or US bearings. No Chinese crap.
- A Heavy-duty SYE ... advance adapters? PORC? My lift will never be over 4", so I don't think I need the extreme short shaft.
- A good driveshaft supplier.

Any other recommendations, while I'm at it?

Edit: I bought a made-in-the-USA Cloyes chain a few years back. Are they any good?

And here is a newbie question ... would it be possible to get my driveshaft balanced with both of the yokes attached? Wouldn't that be a better solution than just balancing the shaft alone?

Thanks.
 
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I have a Advance Adapters SYE kit. (Same as PORC) Much larger output and larger spline count. I just run a front driveshaft in the rear. One spare then. Chain i run a stock HD replacement from crown. No complaints.
 
Chain i run a stock HD replacement from crown. No complaints.

Crown also makes a 231 rebuild kit (231MASKIT). They say it works for 87-2001 xj, but there are 2 different sizes of input bearings in different years (16mm and 24mm). Maybe they just include both bearings? Anybody ever used this kit? How is Crown quality in general?
 
Not trying to be a downer but is there anything wrong with the tcase? Why tear it all apart and have the off chance at messing it up?

If it currently drives fine and you don't plan on going over 35" tires I would just put the SYE on/in and run it.


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Time to rebuild my '91 NP231-J (with the long tailhousing).

I need recommendations for the following:

- Does my version have the 16mm or 24mm input bearing? I think it's the 24, but not sure.
Its probably the thick input bearing; everything changed at about the same time so older tail cone (correct for 91) very likely means older input bearing. It is technically possible to use the smaller bearing with the old style housing, due to the way everything goes together (a lock ring controls depth, and the seal retainer keeps the lock ring from coming back up), but it allows some unintended play at the end of the shaft so better to use the thick one if that's what you need.

- A good rebuild kit with high-quality Japanese or US bearings. No Chinese crap.
The generic rebuild kits are not very good. G2 used to sell one that had Timken bearings, not sure they still do. Call and ask, if yes and its available buy that one. Personally I just order the bearings and seals individually, and if I need any of the plastic parts or o-rings then I will order those from Crown as needed. Timken bearings will either be Timken or a substitute of the same quality (usually Japanese or German). Timken also sells seals but they can be difficult to find sometimes. SKF bearings and seals are also good.

- A Heavy-duty SYE ... advance adapters? PORC? My lift will never be over 4", so I don't think I need the extreme short shaft.
Advance makes good stuff. The top-name brands are all about the same quality. I would avoid any of the budget ones.

- A good driveshaft supplier.
Local anecdote favors Adams, but I've seen about the same rate of failure from all of them.

Edit: I bought a made-in-the-USA Cloyes chain a few years back. Are they any good?
The Cloyes chain I put in my 242 stretched out really quick, can't say I would buy another or recommend them again, unless the only other alternative was Crown or OMIX-ADA, which I know suck. If you can find a Morse Hy-Vo chain that is what I would recommend, think there are some on ebay.

Any other recommendations, while I'm at it?
I bought and installed one of these kits in a friend's NP231, was nice and clean, good upgrade. http://www.ebay.com/itm/172534418223 Make sure you specify old-style (91) when you order, if you do, since the gear cut changed around 95.

And here is a newbie question ... would it be possible to get my driveshaft balanced with both of the yokes attached? Wouldn't that be a better solution than just balancing the shaft alone?
The double-cardan shafts are balanced as a single whole unit. You don't balance the halves separately.
 
Not trying to be a downer but is there anything wrong with the tcase? Why tear it all apart and have the off chance at messing it up?

That's a valid question ... The output shaft bearing is bad, and it has 260k miles on it. The chain is also stretched. My thinking is to just do a complete job and be done with it for another 200k. I've overhauled several motors, brake calipers, power steering boxes, etc. I don't think I'll mess it up if I can get quality parts.
 
Its probably the thick input bearing; everything changed at about the same time so older tail cone (correct for 91) very likely means older input bearing. It is technically possible to use the smaller bearing with the old style housing, due to the way everything goes together (a lock ring controls depth, and the seal retainer keeps the lock ring from coming back up), but it allows some unintended play at the end of the shaft so better to use the thick one if that's what you need.

Yes ... I'll definitely make sure I get the proper size

The generic rebuild kits are not very good. G2 used to sell one that had Timken bearings, not sure they still do. Call and ask, if yes and its available buy that one. Personally I just order the bearings and seals individually, and if I need any of the plastic parts or o-rings then I will order those from Crown as needed. Timken bearings will either be Timken or a substitute of the same quality (usually Japanese or German). Timken also sells seals but they can be difficult to find sometimes. SKF bearings and seals are also good.

Yeah ... I'm definitely NOT looking for generic low-quality stuff. Have you heard of Nachi bearings? I think they are Japanese and OEM for the AX15. Basically ... I just want to do it once and do it right.

Local anecdote favors Adams, but I've seen about the same rate of failure from all of them.

Ok ... Have you ever heard of SBC Offroad Engineering? I had a phone talk with a guy there, and they seem to care about quality.

The Cloyes chain I put in my 242 stretched out really quick, can't say I would buy another or recommend them again, unless the only other alternative was Crown or OMIX-ADA, which I know suck. If you can find a Morse Hy-Vo chain that is what I would recommend, think there are some on ebay.

I'll put the Cloyes on eBay (I haven't installed it yet), and get the higher-quality.

I bought and installed one of these kits in a friend's NP231, was nice and clean, good upgrade. http://www.ebay.com/itm/172534418223 Make sure you specify old-style (91) when you order, if you do, since the gear cut changed around 95.

Thanks. I'll check it out.

The double-cardan shafts are balanced as a single whole unit. You don't balance the halves separately.

Yeah ... I don't think I worded my question well. I was talking about balancing the entire shaft, with the T-case yoke, and the D-35 yoke attached to the shaft. The entire shooting match balanced together. Probably a dumb question. The guy at SBC explained it's just not done like that.

Thanks for your advice (and everyone else's).
 
Yes ... I'll definitely make sure I get the proper size



Yeah ... I'm definitely NOT looking for generic low-quality stuff. Have you heard of Nachi bearings? I think they are Japanese and OEM for the AX15. Basically ... I just want to do it once and do it right.



Ok ... Have you ever heard of SBC Offroad Engineering? I had a phone talk with a guy there, and they seem to care about quality.



I'll put the Cloyes on eBay (I haven't installed it yet), and get the higher-quality.



Thanks. I'll check it out.



Yeah ... I don't think I worded my question well. I was talking about balancing the entire shaft, with the T-case yoke, and the D-35 yoke attached to the shaft. The entire shooting match balanced together. Probably a dumb question. The guy at SBC explained it's just not done like that.

Thanks for your advice (and everyone else's).
Got some Nachi from Timken boxes before. Never heard of SBC Offroad
 
By the way ... my jeep is a 91 Sport, white with red and orange pinstripes like yours. I read your build, and it was like I was looking at my own LOL. I also lived in PG county, Maryland for awhile ... close to DC.
 
I need recommendations for the following:


- A Heavy-duty SYE ... Advance Adapters?

Ran one for the last 15 years or so in my '01. Never given it a second thought.
 
Since your tearing it all apart anyways, look into the hybrid 231 case. I dont remember the specifics but it was a combination of the xjs and a Dakota or s10 231 case that gave you better planetary and a thicker heavier chain and gears if im not mistaken. It's worth looking up atleast

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Since your tearing it all apart anyways, look into the hybrid 231 case. I dont remember the specifics but it was a combination of the xjs and a Dakota or s10 231 case that gave you better planetary and a thicker heavier chain and gears if im not mistaken. It's worth looking up atleast

Yeah ... I have been looking into that. ehall posted a link to a nice beef up kit, which has the beefier chain, gears and planetary: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=172534418223 This kit is for '94-up, but I sent a message to the eBay seller, and he can send me a kit with the right planetary for my '91.

Another option would be to just get an entire 231 from a junkyard S-10 or Dakota, and building the hyrid from that.

I'm also looking into a more direct linkage to replace the crazy Z-bracket setup, like here: http://www.bsfab.net/?p=26. The shift lever from an S-10/Durango would be helpful with that.

Anybody know what years of S-10s/Durangos have the larger chain and 6-pinion planetary? It also needs the front output shaft to have the same number of splines.
 
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for my lsx swap i built an np231 j/c

i used an s10 np231c 1.25" chain and gears, NP241c 6pinion planetary(some s10 231c's also have this, depending on the year they may only have a 4 pinion planetary's)

you also have to pay attention to year cutoffs, i belive its 96-97+have a different gear cut than the older units and they cant be mismatched.

and im using an advanced adapters SYE as well.
 
Ok ... SKF makes rebuild kits that include all roller bearings, needle bearings, seals, gaskets, o-rings, washers, and fork pads. Since it's SKF, I'm assuming it's all high quality.

Here are the part numbers and applications for the kits:

STCK231 - (1987-1994) with the 24mm input shaft bearing (marked BD50-8)
STCK231FF - (1994-1998 & 2000-2001) 231 with the 16mm input shaft bearing (marked 6010N)

Rock Auto has the STCK231 for $102. You can also get a 5% coupon anytime for them.

Also, there is a seller on eBay (powertrainpartswarehouse) that sells rebuild kits that have Nachi Quest bearings. The one for my application is about $80 shipped.
 
And one other point: I have heard that 4- or 6-pinion planets are overkill, since there are other parts that will break first. For my application, I think I'll just stick with the stock 3-pinion planetary, with the 1.25 inch chain and gears as an upgrade -- mostly because I don't want to deal with a stretched chain again. Here's a kit for it:

www.ebay.com/itm/311797379111

I've contacted the seller, and he's willing to sell it without the chain, so I can get a new 1.25" chain.

Hope this helps future searchers.
 
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