T-case swap. Any last advice before I start?

[PK99TJ]

I am going to swap two t-cases:

A 1993 ZJ NP242 4.0L will go into the 1998
The 1998 ZJ 5.9L NP249 will go into the 1993

If there is something I should be worrying about, other than a t-case falling on my chest, please let me know.

I'm of the opinion this should be a direct swap. People are claiming half a day of work, so I am figuring it will be a 2-3 day job for me.

What do you think?

[Jerry Bransford]

Are the spline counts the same? One is the 4.0L and the other is the V8, I thought they used different spline count t-cases. I don't know that for sure, hopefully you have that question already sorted out.

[PK99TJ]

Everything that I read is telling me that they'll both be 23 spline, medium length input shafts, and that the total dimensions are identical, or "close enough". No shortening anything required.

I suppose we'll see. Lucky for me I can hit undo on this project if things go sour somehow, since they're both mine...

I pick up the 98 tomorrow. I already suspect its t-case has a bad viscous coupler, based on my test drive. And even if it doesn't, chances are it will shortly since they're notorious for this.

[PK99TJ]

249 for 242 swap is done!

The only gotcha I found is that the 1998 5.9L ZJ uses 1330 u-joints in its rear driveshaft, unlike every other Jeep in creation. So, simply using the junkyard driveshaft that matched up with the longer transfer case wasn't enough... I had to shorten my 5.9L driveshaft down by 2.5".

That was a lot of fun... hard work but was totally worth it. In the end the donor case came from a 97 ZJ 4.0L. It all worked out beautifully, except for my sore back and beat up hands.