Transfercase solution
 

As you know, I'm working on a 47RH swap into my 92. The old solution was to remove the rear transmission output shaft seal, RTV between the transmission and transfercase, pray the ATF and 75-90 never meet. Any new solutions for mounting the 205 transfercase to the 47RH?

Why not run ATF in the NP-205 then if they swap spit, it is not an issue?
I have seen NP-205s run great on about anything other than air [run empty] or water [mud trucking].

The FSM specifies motor oil or GL5 gear oil. I've read in other applications such as GM, ATF was used. Must have been a reason Dodge specified it, so I don't want to risk using something else.
I was thinking something along the lines of a reduced diameter coupling or different seal.

GM did spec or ATF on the NP-205 they used which is why I just mentioned that that would be an easy solution.
I used the NV-4500 spec'ed fluid in my black '85 crew cabs NP-205 as well, when I did the NV-4500 swap. I did that for the very reason of potentially swapping gear oil into my NV-4500.
I also messed around with the rear trans seal, but can not remember exactly what I did now as it was a few years ago.

If the a518 didnt have the seal and the 47RH is pretty much the same trans with a lock up converter...why worry about the seal? The A518 didnt have one. I was always told it was good to have a spot of fluid in there to lube the output and input splines to keep wear down.

Just replace both seals on the 205 input shaft and don't worry about.

My 90 went 25 yrs on ATF in NP-205. and if it weeps a little it will keep splines and coupling lubed up. I tore it down to replace leaking output shaft seals, there was zero wear on everything except the thrust washer.not bad for 25 years of hard work. just my .02

Nothing wrong with ATF in NP205 your parts. Synthetic preferred.

I didn't know the 518 didn't have a seal. So I'm going to replace the seal in the 205 and seal up the surface between the 2 and call it good.

There are two seals on the 205 input shaft. One facing each direction.