Ok
I know that this has been talked about before but I couldn't find it in the archives??? OK I have a 98 TJ with a 2.5l ax5 and np231. I just got two dana 300 for a great deal, heres the plan (my ax5 got 120k on it and the 2nd gear synco is going as it doesn't let me down shift, soo keep that in mind) I plan on keeping the 2.5l motor, and need a better crawl ratio, that where the dana 300 with lomax gear (4:1). OK here's where the questions start, IT VERY expensive to swap in the Nv4500 sooo have anyone figured out how to shed a few bucks from the swap, I look

Some of the early XJ 2.5l (and 2.8l V6) AMC/Jeep engines used a T5 transmission, this removeable bellhousing may be easier/less expensive to adapt the NV4500 to. (If you find one, grab the slave cylinder and clutch fork, too.)

The early V8 4x4 Dodge NV4500 (23 spline) will bolt to the Dana 300 t-case. The 5.9l Diesel and all late Dodge NV4500's have a larger 29 spline output and would require a new input shaft for the Dana 300. Chevy NV4500's will require a new input, too. (32 spline).

The Dana 300 will need to be flipped to work with the stock front axle, since it's normally used with a passenger side driveshaft, as compared to the driver's side on the TJ.

The stock 231 t-case could be used, but you will need to install the 23 or 29 spline input to match the trans. It would be better to add the HD output with a slip yoke eliminator, along with a wide chain from the Dodge version to beef it up when you install a 4-1 kit.

Another option is a Rock-Trac t-case from a Rubicon TJ, you could possibly find one for about the same cost as a 4-1 kit and slip yoke eliminator. You could sell the Dana 300's and the stock 231 to make up some of the cost.

Hope this helps!

Find a cheaper labor rate...

Seriously, that type of swap has a number of things to address in order to be correct. It is the little things that run the cost up.

I have an NV4500 (along with NP 231C 4:1 t-case) in my 94 YJ. The t-case was more problem than the NV4500.

A different clutch and input shaft MAY be required. (My transmission was previously installed in a YJ and I only needed a new throw-out bearing and clutch.)

You will need a CV-joint on the tail-shaft. I already did that a few years ago with a lift.

Both drive-shafts need to be re-done (shorter rear, longer front). Now is a good time to upgrade the yokes from straps to clamps.

Skid plate needs to be modified.

There are a few interior mods to account for different positioning of shift levers.

Well I have a forgot about the idea of going with the NV4500. I just can't afford it. Its a great trans but for the money it way over kill for the 2.5L. So I am moving forward with the AX5 and Dana300, UNTILL I found that I can put an AX15 in the jeep with a plate made by Adv Adap. HMMMMMMM what do you guys think???, MY thoughts are that is a moderate expense with moderate strength gains???
what do you think

I think the same plate may work for the NV3550 too, which has a bit lower first gear. You will need to swap the input gear on the stock 231 if you want to reuse the original t-case, (23 spline vs 21 spline) Either trans is a good bit longer, so the shafts will still need mods.