speedo cable leak

I've read all the threads related to this subject and have gotten some conflicting statements. Maybe someone can help me with this problem that just doesn't seem to want to go away. Lets start with some facts, I have a t-14 trans with a d-18 xfer. I put 3 1/4 pints of 90wt in the xfer and 2 1/2 pints of 90wt in the trans. as prescribed. The speedo cable entry starts leaking badly, so I drain the xfer and 4 1/2 pints come out. I knew that there was a passage way between the xfer and tranny but I didn't realize that 1 1/4 pints was going to drain directly into the xfer from the tranny. If you look at the side of a d-18 xfer you will see that the cable entry is slightly above the fill plug to the xfer, this seems to be good and the way it should be, but when you fill the tranny it puts the cable entry below the level of the 90wt gear oil. Well no wonder it leaks this is a nonsealed nongasketed entry into the xfer case.
What kind of an engineering genius came up with this design, No wonder jeeps are known for there leaking.
Lets move on to a solution Iv'e heard of an O ring or a silicone sealer of some kind with pro's and con's on both so what works. I'd like to get this problem solved once and for all.

 

I will tell you what I do know about this type of problem. The coupler that screws onto the d-18 has to have an O-ring between it and the coupler. The speedo cable is designed with a waterproof housing to keep water out and lube in at the t-case. In my case, I did have to put a thin rubber washer between the speedo cable nut and the t-case coupling. This connection has to be tight. Now if you are getting gear lube that is climbing up the core and dumping out behind the speedometer head, then you have the wrong core twist. You will have to have a core made with the opposite twist. The core twist is designed to drive the lube back down instead of up. The core has its own lube, and I like to service it with petroleum jelly. Mine doesn't leak so it works for me.

 

What do you think about pluging the hole between the xfer case and tranny so the levels stay where they are supposed to be. This would keep the cable entry above the oil level. I don't believe there is a hole between the xfer case and a t90 tranny.

 

Yep the T-90 does share. Also the T-86.