Citroen C8 Transfer Case Oil Wear Fault

Ugh, sounds familiar. I had a similar issue with my old Subaru Forester. Though the brand is different, the symptoms sound identical: hesitant shifting and a general feeling of something being 'off'. In my case, it turned out to be defective gears in the transfer case causing excessive wear and contamination of the gear oil. Have you checked the condition of your transfer case oil? Is it dark, sludgy, or perhaps even metallic-looking?

Metallic-looking, you say? I haven't pulled a sample yet, but now I'm sweating. How bad was the damage on your Subaru when you saw the metallic flakes? Was it obvious?

Yeah, the metallic flakes were pretty obvious once I drained the oil. It had a shimmer to it, like cheap glitter had been mixed in. Not good. Based on your description, and especially if you find metallic particles, I'd strongly suggest getting it looked at by a workshop ASAP. Continuing to drive it in that condition could cause catastrophic damage to the entire transfer case.

Right, shimmer is a bad sign. Thanks for the heads-up! Dropped it off at the shop this morning. Turns out you were spot on, defective gears in the transfer case. Quoted me 330€ for the repair. Could have been worse, I suppose.