I've developed a whine in a just 10 miles of driving

[Gander]

Could having too much ATF in a transfer case screw something up? I've drained like a quart from a fill plug (2nd time this happens, last time I've had to add like an ounce, so it's random) and since the ATF came out dark I've changed it. I suspect the darkness comes from the clutch material from the gearbox leaking into transfer case.

You’re leaking trans fluid through the T/Case adapter into the T/Case. Common problem. Simple enough fix, just a bit of a hassle to take the T/Case and adapter off to replace that seal.