Transfer case: crack, black oil, shaves.

[Wine_maker]

Hi everyone!

Year ago I checked the oil level in the transfer case of my shorty. The oil is old (5 years I think) but the mileage with it is 30 000 - 40 000 km.
The level was good, the brightness of oil was great also.
When I check it today I found that the oil became totally dark and I found metal shaves on drain cap.
I changed the oil using Eneos, SAE 75W-90, GL-5. But, when I overfill the level, flowing oil was dark again. I think that I should change the oil again after few month.
Also I found crack on the body of transfer case.
Here is some photo:
http://www.nissanpatrol.com.au/forums/attachment.php?attachmentid=47211&d=1405621708
http://www.nissanpatrol.com.au/forums/attachment.php?attachmentid=47212&d=1405621708
http://www.nissanpatrol.com.au/forums/attachment.php?attachmentid=47213&d=1405621708

So, I know that the dark oil and metal shaves in the oil is bad. But what do you think, how fatal it in my case?
Is the body of transfer case made from aluminum or cast iron? Should I weld the crack or it is not so big problem?

[my third 256]

if it is'nt leaking
i'd leave it alone and start to look at getting a replacement
or even a blown one and then you can use the casing
there is such a thing called metal putty could try that
47219
ur do a search matal putty

[Parksy]

I wonder what caused the case to crack? Has the transfer case come into contact with something solid while moving? That bolt head would be the first thing to be hit, which could have caused it to crack possibly?

Edit, if you were reversing that is.

[Col.T]

G'day wine man,
from the photos it doesn't look like you've hit anything. Can't imagine it's a metal fatigue issue unless that one bolt has been massively overtightened and it doesn't seem to be as there's no apparent distortion. That's just a bit of a guess though. Looks rather like a manufacturing fault.
Use a steel screwdriver and drag it REAL hard over the case. Aluminium will get scraped off much more than steel so you should get an idea what it's made of pretty easily.
When you change oil there's always a bit left in the case so the new oil may well be a little discoloured. I don't know why trans case oil should be really dark though. Never had that on two models. Shouldn't be running at a temperature high enough to cause carbonising/blacking unless there's a real major problem surely.
Reckon I'd run it a while and keep checking the oil colour. If it blackens you may be up for a take out and inspection but I'm not experienced in that.
If the case comes off, get the crack fixed otherwise keep a real sharp eye on it. Third man's suggestion may well be worth a try in the meantime.
Luck,
Col