Turbo 400 transfer case speedo housing issue

[JFORRESTERSR]

So after all the leaking issues and replacing the adapter sleeve and adding orings and so on. The light bulb went off. ding ding ding
the issue is not the adapter or the adapter sleeve the issue is the speedometer gear coming out of the transfer case. Its the only thing that has not been changed and yet i still have the same issue.
So can anyone tell me where i could possibly get a new speedo gear.
and it just basically sits in sit the transfer case, is that correct or should there be some sort of retaining

on a side note I am looking at replacing the transfer case with a zumbrota rtc205g they are saying its a direct replacement does anyone have any experience with them

thanks again all for the help and support