I'm looking for heads-up info from any of you out there.  

I'm about to swap a YJ's 231 21-spline into my TJ that has a 231.  Are the splines of my TJ's input shaft 21-spline? Is it possinble to swap the T-case without dropping the Xmsn too?  How long would a shop typically say it'll take them to do?

(This is the source from my recent postings.  I FOUND IT! Well, I was neglecting the thought of this effort, but other things were fixed.  No loss of efforts, just money from a tight budget.)LOL  

FYI... This is a continuation posting from... "Front Drive Shaft Noise! help?!"  

The TC will just drop off the tranny. You just need to support the tranny for removing the TC. Pretty simple effort.

The 231s are both substantially the same. The two big differences are the input gear spline count and the speedo drive in the tail shaft housing.

If the YJ 231 has a 21 spline input, then there is a good chance it also has a mechanical speedo. So, you'll need to swap the speedo drive in the tailshaft housing.

The 21 spine 231s did not come behind the 4.0L HO. Only 23 spline.

You can swap your input gear from your TJ 231 to the YJ 231. That is also an easy swap.

Once you've done the input gear swap, you have done almost the same work as a SYE. You might consider adding an SYE at this point and replacing the chain.  

I'd also suggest looking into the TJ 231 to see if you can determine what is wrong with it. Maybe it just needs a chain.

The TJ has an upgraded main shaft, making future upgrades to a SYE easier. (Needle bearings don't need changed over).

Rebuilding a 231 is actually quite simple if nothing is totally destroyed.  

So...
1. The YJ 231 has 21 splines whereas my TJ il6 4.0 231 has 23?  Easy swap of the input gear? Do I need to open the case?

2. i do have a SYE for the rear output.  Can the mechanical speedo drive be done while switching my SYE over to the YJ 231?

3. Is replacing the chain do-able for a first timer?  

In response to your second post.  I was thinking of opening it up myself at first.  Would it be recommendable for a DIY. I am comfortable with it all, but don't have all "the special tools".  

Heavy duty snap ring pliers and a clean work bench. If you just pay attention and lay things out in order, take some notes and snap a picture or two, it's super easy.  

So...
1. The YJ 231 has 21 splines whereas my TJ il6 4.0 231 has 23?  Easy swap of the input gear? Do I need to open the case?

2. i do have a SYE for the rear output.  Can the mechanical speedo drive be done while switching my SYE over to the YJ 231?

3. Is replacing the chain do-able for a first timer?  

The input gear is sitting in the planetary gearset. There is a snap ring on the front bearing retainer that holds it in. After removing the main shaft, you can remove the planetary gearset. Then, there is a snap ring that holds the input gear into the planetary gearset. Remove the snap ring and pull the gear out.

Swapping the main shafts at this point is easy. You don't even need to remove the stuff on the main shaft. It is the mainshaft that is your SYE. Combined with the different tail shaft housing which also holds your speedo drive.

The chain comes off first. It just slides off both the front output and the rear output at the same time. You remove both the chain and the sprockets together. Nothing holds them, they just pull up.

After you start into the case you'll see. And, when you get done you'll say wow, that was easy.  

Thanks ftgiles,  You've been helpful in the past, and you're continuing the trend.  Thanks so much.  I'll post how it's all going.  Time-wise!!!!  

You need new snap rings. Don't re-use the old ones. I have found it easyiest to spread the snap ring with the snap ring pliers and then grab it with some heavy needle nose pliers, and bend it and pull it off. Don't try to remove it using just snap ring pliers. The plier tips just keep comming out of the snap ring when you try to pull up.  

Ok, got it.  Three more questions...

 Do you think I could just use some needle nose pliers
for the snap rings as I do when doing u-joints?

 When opening up the case, should the rear of it be facing downward?

 Is the speedo drive what i've removed in the past from outside of the unit while the unit is installed?  

The front half of the case will be laying on it's face most of the time.

The snap rings are big and strong. There is not a lot of room between the snap ring and the face of the gears to be able to get hold of the snap ring. I'd say no. Harbor freight sells heavy duty snap ring pliers for $10. In fact it is a whole kit of snap ring pliers.

Yes, the speedo drive is removable from the side of the tailshaft housing.  

Here it is the 25th.  No not fixed yet.

A planned trip to Pismo was calling not to be cancelled.

Well driving it up there, duning around for 3 days and driving back down.  (11 hrs. pavement time and endless hrs dune-time)  Obviously it's worse.  Oh, the things we do to tourture ourselves!!!

As I get a chance in the next week or two.  I will have the t-case dropped and back into my hands.  I would say what I expect to find, but I won't jinx myself yet.

I'll catch up to you soon.