Easy gen2 231 t-case swap, why haven't I seen this done?

[gavio]

When I was doing my t-case swap, what I thought I learned was that all 231c cases have the yoke on the front output, so you'd have to mod the front driveshaft to work..... SO I put in a 233 and hooked up the electric shift 'cuz I didn't have enough fab skills to pull off a manual shift conversion (JOR kit wasn't available back then).....

So now my encoder motor died.... of course.... Not that I can complain, $15 at PnP and it lasted 5 years.....

However.......

In researching 4x4 issues, I find that there was an option on 95-97 Blazers and S-10s for a manual shifted 4x4 system, that uses a 231 t-case with a splined front output.... It's a direct swap for the 233c case.... And better yet, it uses a cable shifter, so it sounds like it should be a piece of cake to mod for an Astro (Jeep and S10 guys do this swap a lot)..... And now I'm curious why I haven't seen it done? You could do it for less than the cost of the JOR manual shift 233 kit and would have a super slick factory look (especially if you used the shorty shifter console that comes in bench seat models) and would be smoother shifting to boot.... The option is rarer than the electric shift version for sure, but out of curiosity, I looked on eBay and there's about a dozen of them for sale right now..... If I would have known back when I was doing my swap, I'd have done this in a heartbeat, I've seen at least 8 or 10 of these in Pick-nPull over the last few years without knowing what I was looking at....

The only thing that makes sense for me right now (I live in my van and don't have a place to work) is to just buy a new encoder motor and carry on, but damn, I would get at least some vicarious satisfaction out of seeing someone else do it....

With pictures....

Or finding out why it doesn't work, so I could at least be happy I didn't do it.....

[WimpTech]

I don't recall ever seeing a manually shifted S10 or Blazer on my trips through junkyards, might be a rare duck or something. Thanks for the tip, added to my JY search list to research.

[gavio]

I actually took parts off of one, and I remember thinking a Blazer with a bench seat was unusual, but I didn't even notice that it was a second generation Blazer with manual shifted 4x4.... I've seen others, too, but still didn't register..... Wish I would have checked it out more.....

Anyway, yes, they are relatively rare, but this is by Chevrolet truck standards, so they are certainly not nonexistent....

[Leeann_93]

Earlier 90s Blazers etc had levers on the floor for the t-case, just the later ones switched to the buttons. My '05 Jeep Liberty has a lever on the floor and an NP231 t-case.

[jmderyke]

I think those transfercase has a different spline out put count.....if I remember right. Might be able to swap a different output shaft but just easier to just go with the 233c. And the 233 in super available for cheap while being exactly the same as the 231 internals

[gavio]

All the earlier S10 and Blazers used a floor shifted 231c transfer case.... It's a lever operated shifter and the t-case has a yoke for the front output.... It would take a lot of work to make that fit in a gen2 Astro....

But, what I'm pointing to is that in the years 95-97 or thereabouts, the gen2 S10s (the rounded ones) had an option for a floor shifted 4wd system that uses a 231 transfer case that has a spline output at the front.... According to the S10 guys, it's a direct swap for the 233c (which is what the majority of them were ordered with, electronic shifting being the latest rage at the time).... And it uses a cable shifter so should be relatively easy to use for swapping....

Here's a link to one on eBay for reference, note the spline output and the tag which reads 231....

https://www.ebay.com/itm/TRANSFER-CASE- ... pQ&vxp=mtr

[akforceten]

Since the 233c is cheaper and is easier to find for me and it's super easy to convert to make it a manual shift.With a lot of wrecking yards not keeping the older S-10 trucks and blazers, the 233c was my best option and since I was there I also looked for a floor shifter out of something else total cost was around a $100 and a little time

[gavio]

Welp, this idea just wouldn't leave me alone.... Plus which, I got tired of holding my breath every time I pushed the button to see if it would go into 4WD or not..... So I picked this stuff up the other day....

I got this case out of a 95 Blazer, from a year I found on car-part.com..... It' is indeed a 231C with the front output like a gen2 van:

It has a 32 spline output shaft:

And as far as I could tell is a direct swap for the 233C..... This is also what the S10 guys say....

Then I went to Pick'n'Pull and found the shifter and whatnot in a 96 Blazer.... Here's what it looks like in it's native habitat:

It took about 30 minutes to get it all apart, and heres the resulting pieces:

The shifter itself is pretty compact, most of the bracket extensions are just for the console.... The shifter also has a range switch with a signal wire for each position, as well as a 4LO signal wire for the ECM:

And the console has this 4WD indicator light that is operated by the range switch:

And the last piece is this bracket, held on by the t-case mounting bolts, which is where the lower end of the shift cable is clipped:

Soooooo, we'll see how it goes.... I hope to get this done in the next couple weeks and I will let y'all know what happens....

[WimpTech]

Holy crap that's hopeful for sure! Can't wait to see

[Mmusicman]

Well this option is certainly interesting and hopeful... provided the drive-shafts fit.
I've read the 231 may not be as strong as the later model 233 (chain size) ..
but if true still more than capable for typical 4x4 use.

We await your progress and results....

[gavio]

Quick update, this does indeed work..... It's turning out great..... I will put up a separate thread in the next few days with some pictures to make it real......

Meanwhile, I'm selling my 233 case for a very sweet deal for anyone wanting to go that route, which also works out very nicely...... SO many ways to get real 4WD in an Astro

[TurnNburn]

I've read the 231 may not be as strong as the later model 233 (chain size) ..
but if true still more than capable for typical 4x4 use.

Yes and no, most 231s have a 1 inch chain and most 233s have a 1.25 inch chain. However, there are heavy duty variants of both (although I have not personally seen this option before, they do exist), and both non-hd's can be built into HD units with the right parts, which are expensive, but available.

[gavio]

most 231s have a 1 inch chain and most 233s have a 1.25 inch chain.

To be more accurate, Jeep 231s (the most common by far) have a 1" chain and 3-gear planetaries, unless it's the HD version..... Dodge and Chevy 231s are likely to have beefier internals.... I read a fair amount online before doing this, and all the examples I found showed GM and Mopar cases with 1.25 inch chains and beefier planetaries.....

The case I got was from a 95 Blazer and has the 1.25 inch chain and 4-gear planetary..... Same as the 233....

[Mmusicman]

I guess the advantage of this rare older 231 case is that it comes with correct splined front output to match the Astro, and it's already manual shift? And this particular model has the beefier parts too?

There could potentially be a case "indexing issue" too.. we'll watch for your results.
If driveshafts have to be corrected for, then it could get a little more complicated and expensive.. and would be a deal breaker.

The 233 case is a direct bolt in, other than converting it to manual shift, which is quite easy and why it's so popular.
I too have wondered why the 231 is not more commonly used.

But options are good... there's always more than one way to do things which is good.
If you got the stronger wider chain, then that's good too.

We'll be watching your progress.

[TurnNburn]

my old 233 I just pulled out (due to noise) and replaced had the 1.25 inch chain but only a 3 gear planetary

[gavio]

There could potentially be a case "indexing issue" too.. we'll watch for your results.
If driveshafts have to be corrected for, then it could get complicated and expensive.. and would be a deal breaker.

The main reason I read up so much online before doing this was out of concern for the indexing issue..... I could find no evidence anywhere that there is any difference between early and late 233 t-case housings that would cause issues..... All reference to indexing issues seems to come from that one build over at the other forum where he had to notch his crossmember for the front driveshaft ..... I think what happened there is more related to engine and tranny mounts and would have happened if he'd used a newer case as well.....

Anyway, this particular variation of the 231c is a direct swap for the 233c, and even uses the same back case half.... I have mine installed and driving around happily..... And since it's a 231 with the neutral position, it should work easily with any shifter and linkage from a Jeep or Dodge or whatever that came with a 231.....

[gavio]

my old 233 I just pulled out (due to noise) and replaced had the 1.25 inch chain but only a 3 gear planetary

I did read some speculation that New Process tended to build cases with whatever they had available at the time, so it would seem there is some randomness in internal configuration.....

[TurnNburn]

That would make sense. I mean, its the only explanation that I can come up with why there would be a difference in chains at all. not to mention number of planatarys.

The indexing issue comes from the transmission to t case adapter plate, and not from the t case itself. That's why every astro that cam with a BW that I have 4x4 (or outfitted with the 99+ 136) swapped had to have shims put under the tranny mount to lift it up so that the drive shaft would clear. I would expect, but have not done this myself, that the if you swapped that adapter plate from a 99+ onto a 98- that the indexing issue would not be an issue.

[WimpTech]

Pleeeease tell me you are working a thread for this mod?! I already got a 233 so I'm still going that route, but this is pure gold my friend.