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My Overdrive has left the chat….

In the 70s those had NP205 or NP 203 transfer cases, probably too big for a CJ.
A Dana 300 with an adapter would fix that issue. And yes, it would another part to get, the square body won't have that transfer case.
 
I installed the intermediate gear with the taper bearings yesterday, and then put the transfer case in the Jeep. A few things I learned:

1. The adapter to the SM420 won’t clear the nut at the pin next to the bottom mounting hole. A little work with the angle grinder using a gasket for a template and it cleared the first time. I even have enough room to turn the nut to add a little more preload if necessary by turning the nut with a big screwdriver using the castle nut and the edge of the adapter. I also installed the cotter pin from the passenger side so it could be removed to turn the nut. Not sure this will ever be needed, but it’s possible with the removal of a material on the edge of the adapter.
2. Since the new pin has a shoulder that stops the pin on the rear of the case and a preload collar on the front of the pin to set preload, using this kit will work on a transfer case that has gouging on the inside of the case where the intermediate shaft sits like the pictures I shared earlier. The new taper bearings don’t use the inside of the case to align the bearing, rather uses the pin on the rear of the case and a collar on the front of the case to preload the bearing. As a result, using this kit would save an otherwise useless case because of the needle bearing failure that gouged the case.
3. I used Right Stuff on the outside of the case instead of the o-rings to seal the pin. I stopped using the o-rings a long time ago since I could never get them to seal and the rear o-ring seemed to always get cut during installation.
4. I had to use a dead blow hammer to seat the pin at the back of the case on the shoulder. Not sure why, but the shoulder of the pin didn’t hit the case when I first installed. A few taps and the pin seated on the case.
5. The bearing races were a tight fit, so using an aluminum bearing driver was required to tap the races in place. This tells me the pocket in the gears were likely cut correctly.

I built a jig using wood to hold the transfer case at the correct angle while I slid the case onto the bearing that I had already installed on the shaft. Having a lift and air over hydraulic lift jacks that slide along the inside of the lift made the actual install a 5 minute job.

Since my case has been sitting in the second floor of the shop for a few years (and I didn’t cover the holes at the end, duh), I’m going to change oil two times rather quickly. I cleaned the inside of the case with spray cleaner and didn’t see anything come out, but changing the oil a couple of times will be a good idea just in case.

Today I will build the new cross member, and will post those pictures in my build thread.
 
I had very poor luck with that kit, bearings only lasted about 15k miles. I'm running Novak’s intermediate shaft now.
The tapered bearing intermediate shafts are not an install and forget about them. You need to pull the pan and reset the preload at about 5k miles and then again at 10k about intervals. If you run them loose, they will indeed go to crap. I ran the first tapered shaft in my 3B for at least 15 years, only replacing it when the TeraLows went in (which also have tapered bearings).

In addition to Nick's comments on the 1 1/8" versus 1 1/4" cases, the other really big difference in my experience is the former almost always have the 2.43:1 gear set, the spur gears of which are not nearly as beefy as the 2.46:1 set found on the 1 1/4" cases (and no doubt why Dana changed the gear set).

I'm another that hasn't destroyed a D18 despite running some significant power in front of them. With the caveat you break anything if you try hard enough, the large index cases are good for at least 450 ft-lbs.
 
The tapered bearing intermediate shafts are not an install and forget about them. You need to pull the pan and reset the preload at about 5k miles and then again at 10k about intervals. If you run them loose, they will indeed go to crap. I ran the first tapered shaft in my 3B for at least 15 years, only replacing it when the TeraLows went in (which also have tapered bearings).
I could never figure out a way to access the adjustment with the transfer case in the Jeep. So, if I have to pull the case every 10k, not gonna happen.
 
I could never figure out a way to access the adjustment with the transfer case in the Jeep. So, if I have to pull the case every 10k, not gonna happen.
You could not access the shaft nut on the front? Maybe I'm just lucky with the adapter I'm using. The entire system would work better if the shaft install was from the front and the adjustment on the rear. That is what Jeff Petrowich was working on but I don't think that project went anywhere.
 
You could not access the shaft nut on the front? Maybe I'm just lucky with the adapter I'm using. The entire system would work better if the shaft install was from the front and the adjustment on the rear. That is what Jeff Petrowich was working on but I don't think that project went anywhere.
I mentioned in an earlier post that I used an angle grinder and an extra gasket on the Novak adapter to allow me to adjust the nut. I also paid attention to how I installed the cotter pin so it could be removed without pulling the transfer case.

I actually adjusted the preload one notch on the castle nut after the transfer case was installed, as I wasn’t sure the pin was fully seated. I tapped on the pin and adjusted the nut with a large flat bed screwdriver, so I know I am able to adjust the preload with everything installed.

My biggest challenge is that my Speedo cable is broken and I’m too lazy to replace it, so I will have to adjust at 5,000-ish miles.
 
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