np231 questions

[gus310]

as my plans grow for my jeep, they all meld together, currently im planning and gathering parts for my xj rear spring swap. and have begun thinking about the slipyoke install. but over the last few weeks ive been thinking about dual cases. in my research ive found that a chevy s-10 came with an NP231 with a wider chain. this would make the 231 more durable to the stresses of low gearing and the torque multiplication that comes as a byproduct, also, it would hold up a lot better to the bigger tires i will be running in the spring.

so my question is, i couldnt imagine there would be too many differences between the two cases, both being out of two light duty trucks. does anybody know if there are any?

second, as far as spline counts for the 231, there are 21 and 23 spline shafts. how can i tell what my 1994 wrangler's 231 has in it for a spline count short of removing it and counting them?

does anybody know off hand which year s-10 would have 23 splined shaft with the wide chain? or how i could find that out?

[2000Cherokee]

gus310 said:

does anybody know off hand which year s-10 would have 23 splined shaft with the wide chain? or how i could find that out?

your best bet would be to find a chevy oriented board. they would be of more help than here most likely.

sounds like an interesting swap though..

also i dont know if you have looked into it but JB conversions sells a wide chain kit for the NP231. i belive its around 300 bux. give or take a little

[gus310]

i think the chevy 231 is a 27 spline so i would have more mods to do just to work it nevermind any electric connections that may be different. also i found the dumb answer i needed, apparently the 4cyl 231's had 21 splines, the 6 had 23 splines. car part could only find a 231 with a $400-500 price tag. f*** that, ill find one on a local forum for cheap. anybody here got one?

[2000Cherokee]

have you looked around at your local junk yards? you could also cheock other online forums

[Twisty]

john might know about the spline numbers.

[axle]

Check NEZR2's site.

[jps4jeep]

Gus, Unfortunatly I don't know off hand the spline count on the np231 in S-10's I can find out when I get home.. also, only older S-10's had the NP231, 93-ish/94ish there was a mid year change to the command trac or what ever they called it.

As for your Jeep, I need to know the tranny you have.

IMHO, a doubler is a great way to increase your gearing option. but.... In a Short Wheel base jeep, could be difficult.. all depends on you lift amount, the distance you stretch your wheel base, and you t-case choices. if you were to do a doubler, and this is all second hand knowledge so someone correct me if I am off kilter, the toyota doubler system, and the 205/208 doublers are worth the money and time investment. from what I have read (mostly on pirate) the np 231 is not worth it.

If you were to do a 205/208 your Tcase length is gonna be long... you will probably have to consider a wheel base in teh area of 108" or greater. (My estimations are from this math: stock wheel base minus the length of a stock np 231 plus the combined length of the doubler, add extra 5 inches for a CV style D/S)

For the money and time and everything,

My two best suggestions would be.

1. Look for a used Atlas 3.8, now that three and four and ten speed tcases are all the rage, the old 2 speed Atlas's are gonna come down in price big time. the 3.8 being the cheapest, as well as still offering a good choice in crawl ratio and wheel spin when needed.

2. Look into a flipped Dana 300 with a tera-lo 4.1 kit. I have seen a couple on Pirate for sale (if memory serves me $ 700-800) and is a very strong T-case. You could build one with an exhisting D300 for about $1200 ($700 tera-lo and $500 for the flip kit)

[jps4jeep]

smart trac, not command trac...just thought of that.

[2000Cherokee]

you could also check into the stak 4x4 t-cases.. i have heard good things about those as well

[gus310]

the np231 is a strong case and once im geared in the axles with bigger tires, i wont have to drive so heavy on the throttle. that said, the dual cases will provide me with a stock 2.72 to 1 crawl and when the second case is engaged, i will have a 7.4 to 1 ratio in the tc's. giving me an overall crawl ratio of 138 to 1... ;D

the other issue of money, is i can find another np231 for around $100, the box4rocks dual case adapter has been used now for a short while and ive only heard good things about it, costs $399, and ill need a new driveshaft at the price of about $300. plus steel for a new crossmember, call it another $100. and thats about $900, and gives me multiple chopices for gearing.

ive been gathering parts for an xj rear leaf swap, and im almost ready to install. fuel cell, used lifted xj rears, ford 9" with 4.88 gears and a lockright. new brakes on the axle, and a dodge front shaft with a cv, to go with my sye.

the stretch will give me plenty of room for the cases, so thats not a concern, and dual cases with the sye will be about the same price as the 4.0 gears for the 231.

[jps4jeep]

sound like you have a plan, but the strength of a np 231 is marginal. chain driven, and aluminum casing. Any iron case and gear driven case would be a lot stronger.

as for the length, I still think two np231's, even with a sye, stretch, and the amount of lift might be on the long side.

You want to do it, go for, I say prove me wrong.

another idea would be if you jeep is not a Daily driver, look into a sm420/465, with a stock 231, your gearing options will be similar to what you want to achieve with a doubler.

[jon]

Alright, So I am kinda new here, but Todd told me to swing by and check it out.

I met a few of you guys yesterday.

so here's some answers to some of the questions and misinformation on here.

the s10 231 is pretty beefy. it has the wide chain and the 6 gear planetary. Pretty much the smae internal components as the 241.

problems are its 27 spline input and usually have a 5 bolt front pattern.

Byt 205/208 doubler I assume you mean the 203/205 doubler. this is a pretty crappy setup for a jeep. its wicked heavy and only gets a 4:1 ratio. Wicked strong though so good for a full size.

the 231 is plent strong. especially if you put the 6 gear planetary in it.
IF you want a 231/231 doubler. use a stock 231 front and a 231 with the HD gears and chain behind it. if the second case has a SYE they are almost the same size (with a 7:1 ratio)

ideally and what I plan on doing is a 231/ dana 300. I am doing this fairly on the cheap as I will do all the machining for the kit flip kit. A good buddy of mine already did a 241/300 doubler. and it really isn't that hard. Right now I am into the whole shebag about $80 and that is for a 231, and chevy 231 HD and a dana 300. I have the material to do the rest.

I have a the wide chain and sprockets from the 231 HD if anyone is interested as well. I don't need it.

[jeepgod]

jon said:

Alright, So I am kinda new here, but Todd told me to swing by and check it out.

I

don't bring me into this

[jon]

I figure that would warn everyone that I am an obnoxious drunk a******

[jeepgod]

jon said:

I figure that would warn everyone that I am an obnoxious drunk a******

ok, thats funny ;D