ATF/Tranfercase leak

[polyarkos]

Hi All,

Is it possible to have your transfer case oil leak into your auto gearbox?

I only ask as I've just done a filter and ATF flush as well as the transfer oil. When doing the transfer case the oil came out looking pretty dirty and milky, and now I've done the ATF it was really dark, almost black. I tried to completely flush the ATF using the cooler lines but after 12L it is still quite dark (not pink like the fresh stuff).

Truck drives fine, but I'm wondering what would make these oils look so bad?

[geeves]

trans oil gets darker through long term use but black suggests the box has overheated or is slipping. To flush the box can take a lot more than 12l as the new oil mixes with the old and what comes out is a mix. If the oil was changed every 30000km this problem pretty much never happens(My wizard oil was still redish after 50000km plus whatever the previous owner did since the last change)
transfer case is a separate unit. It is possible to leak into the trans but I would expect it to also leak on the ground if it did. It would have to get past 2 seals. Milky suggests water

[polyarkos]

Great. Looks like I'll change the ATF fluid again after a couple of weeks. Gearbox drives well, just a little flaring going from 3rd to 4th at 80km/h+

[geeves]

thats normal for these boxes. Its worse when cold