Just my thoughts on it.
They say if the domed end caps are not busted, that's good.
I would hesitate to open it up. If you know the history of who had it first, that helps in my opinion. Forest service, utility, railroad, loggers, I.E. big 4x4 user. Otherwise transfer case's don't get 500 miles on them. These have big gears and big bearings. I have one also. I don't want to make it leak by "looking inside". But I would have to take it out to look, you don't.
You may hardly use it. It may be just fine. If not, fix it then, it's all removable from under.
There are videos and how-to's for it. It's kind of straight forward old fashioned American gear train, bearings and seals. There are rebuild kits for it. ($300)
I don't know if you have ever run it. If you have and it works, Leave it alone. I have tried mine and it seems to engage and etc. Change oil and.......
You can fill it and run it in "no load" mode to get oil to long-time-dry-bearings. Then drain and refill. Not dangerous, only install the input drive shaft. It won't go anywhere. Listen for noises. (gears were noisy in those days). Low speed of course. Test for heat. (but I don't know if your motor and transmission is in?)
Most folks put a pipe street elbow in the filler hole so as to "overfill". It seems like the design was not optimum for oiling everything. Overfilling to a higher level won't hurt it at all. Do that for sure.
>>>>>>>Rebuild Manual<<<<<<<Filler Elbow
