2000 tahoe with 4l60e transmission, has fluid migrating from transmission to transfer case. Replaced transfer case input seal 2 months ago, problem persisted. Now replacing transmission output shaft seal as well. The old seal and all surfaces appear to be in really good condition, and I am wondering if there are other potential causes for this problem before I put everything back together.
that's pretty much it. Most seals work one way. to keep the fluid in. If they leak the fluid gets out. because the area between the trans and transfer case is seal up between one leaking out will usually end up in the other.
there shouldn't be any other places where they would be combined to create a transfer from one to another.
Well, unless someone tied the vent hoses together. Just kidding...