Yes I've researched the topic: Transfer Case Upgrade to 6-Planetary Gear NP231 Tech Thread np 231j upgrades - Pirate4x4.Com Bulletin Board
I got the 231 out of my old XJ after I scraped it and am looking at doing a few cheep upgrades. Top of the list is a JB conversions SYE, since the t-case had a hack n tap. Next on the list is a wide chain and 6 planetary gear conversion. The t-case is in need of a new chain anyway, after being run in FWD for the last 6 months, after the rear end bit it and never had the time to put it down long enough to fix it.
Since I'm looking to do this cheepish, I'll be getting the needed parts out of the JY. Since I'm cheep, I'd like to eliminate buying as many transfer cases as possible. Don't worry, the money saved on buying only one case, is being spent on a full rebuild. So by process of elimination, this leaves me with trying to find the NP231C with the 1.25 wide chain and 6 pinion planetary set. - EDIT: The NP231C only came with a 4 pinion planetary.
Here comes the questions: The most specific info I've been able to find on the 231c is "from an S-10, forget the year, early-mid 90's I think." anyone be able to give me anything more specific?
Also, it seems that all the write ups I've found involve using a pre 96 231J case with a 241 planetary set because "Somewhere between '93 and '98, the gear cut changed, so the six pinion planetary I had procured would not mesh correctly with the gear in the '98 case." Does anyone know if the 231C from the "early-mid 90's S-10" planetary's will work in the 96+ 231J?
Well since no one has been able to help, I'll help you with what I've found:
From what I have been able to gather, the most strait forward way to do this is with a NP231D HD out of late 80s- early/mid 90's V8 Dakotas and 1/2 ton Rams, with 4WD obviously. The NP231D HD came from the factory with the 6 pinion planetary set and wide chain, and is the closest to the NP231J, but with provisions for the vacuum disconnect. Since I'm still not sure if the planetary gears from the 231D will work with the 231J ring gear, I may have to get a early 90s 231 out of an XJ at the JY for the front half.
I can't give an absolute on what to find it in because I found my transfer case laying in one of the isles at the JY, already pulled. Although there was a early 90's Dodge Power Ram missing it's transfer case near by. I didn't bother to look to see what year it was though. I have been told that the 97 V8 Dakota is known to have it, if that helps.
I've been able to get a few deals on some lightly used parts that I thought I was going to have to buy new. Like a great deal on a JB conversions SYE and a Tera 2Lo.
Junk yard NP231D HD- $120
JB Conversions SYE- $100
New NP231D HD replacement chain- $55(Cloyes P/N 10-022)
Tera 2Lo -$100
NP231 Rebuild kit- looks like my cost will be around $65
All For a little more than the cost of a wide chain conversion from JB Conversions, by itself.
I'll have more info as soon as I get both transfer cases together for back to back comparison.
I've got both t-cases now, but had to make a change to the parts list. The guy that was going to sell me a JB Conversions S/S SYE had to back out. I did end up talking to Imped and we've worked out a deal that I'll buy his JB SYE, so he can get a JB S/S SYE.
Since the Wrangler this is going into will have about a 10" rear stretch, I don't need the S/S SYE.
I should start pulling them apart soon, so I can check the fitment for the planetary gears, and throw the cases in the hot tank at school and clean them up. I'll be taking plenty of pictures for the right up, and to remember how it all goes back together.
Started screwing around with the 231 HD today and found that I should be fine with the planetary ring gear, I saw on the tag it was built 11/13/98, what ever it came off of was probably a 99 or 00. No pics, I really need to suck it up and buy another digital camera. I'm far from done so there is plenty of time to get more pics. Going to finish pulling the guts out of the HD case, and take all the case parts with me to school to see what good the hot tank will do for them.
But looks like some good information here! Any plans for lower gearing?
I've been given a couple of trashed Tera 4:1s, and one of them I can get Teraflex to rebuild for a great price. But no, Not looking for any lower gearing right now. I'll save that for when I can get an Atlas 4, I like my 2.72:1 about 90% of the time, it's rare that I wish I had more gearing. Besides, the 4.7L stroker thats going in front of this should give me plenty of torque when I want it.
Originally Posted by ytowntj
But your doing so good on your own
For real keep us updated, Ive been looking at doing this eventually.
Absolutely, I've yet to find a write up on it being done using a 231D HD, so I wanted to make sure I did one to get the info out there.
On a side note, here are some of the differences between the 231J(Jeep) and 231D HD(Dodge V8):
The Jeep(bottom) was a attempt at a hack n tap SYE, until the drill bit broke off in it(why it was free). Dodge also uses the old XJ and YJ style tail shaft that requires the drive shaft it be in place to seal the case. You can also see the wider sprocket on the dodge for the wide chain.
The chains, Jeep(bottom), and the Dodge chain. The Cloyes P/N for the wide chain is 10-022.
Edit: Just noticed I didn't put up the pic of the Dodge and Jeep chain, fixed it.
The D case has the wider chain, not the J. I haven't had the chance to compare the front half of the D case to the front half of the J yet, only a Tera 4:1, but so far, none of the cases look to be larger than the next, only the internals are differing. I'll have a few more pics tonight.
Wednesday I'm taking a bunch of aluminum to the scrap yard.
So in light of the planetary set being 3 pinion instead of 6 like I had hoped, I'm going to forgo that mod unless a 6 pinion falls into my lap. Also, pending a back to back comparison of the Dodge and Jeep cases, I think I may just use the entire 231D HD, save for the addition of the JB Conversions SYE and Tera 2 low. That allows me to cleanup the XJ t-case and sell it, to fund other parts of the build.