XC90 Gearbox Slippage

That sounds very familiar. I own an XC90 as well, and I had similar shifting problems a while back. Is there any sign of oil leakage around the transfer case itself?

I haven't noticed any apparent oil leakage, but I'll inspect more thoroughly. Do you recall what the root cause was in your instance, and were there any other indicators besides the shifting issues?

In my case, it turned out to be defective gears within the transfer case itself, resulting in the oil wear fault. No visible leaks, just mechanical wear. I'd recommend having a workshop take a look; might save you a headache.

I appreciate the insight. I took it to a reputable workshop as suggested, and the diagnosis aligns with your experience: defective gears causing the oil wear. Repair cost is estimated at 330€. Thanks again for sharing your experience; it helped immensely in understanding the problem.