Trying to fix leak/ brakes?

[Jered1987]

I have a 350/th350 and I think maybe a np203 transfer case not sure.
Anyways I have a heck of a leak the truck sits at my wife’s grandparents house for a while at a time but when we go back the leak is so bad I have to put a whole gallon of atf fluid in just so it will move. I’m planning on trying to take it out I’m wondering what the most common culprit is seal or gaskets? Also wondering how to take it out, any help recommendations on removal and install and if it’s not gaskets how do the seals go in?


Also the picture I put in for the difference in brake calipers...will the new one work or not? I got one for a 85 k20 since the guy at advance said they would need one for a 2500 with it having a 8 lug conversion.