Mercedes E Klasse Diesel Transfer Case Issue

That sounds rough. I had similar issues with my older Audi Q5, though it was a petrol. Slipping gears, jerky shifts, the whole nine yards. Turned out to be gear wear inside the transfer case. Have you checked for any signs of oil leakage around the transfer case? Also, what does the gear oil look like? If it's dark or has metal shavings, that's a bad sign indicating mechanical wear. An oil change might help temporarily, but if the gears are indeed defective, it's just a band-aid. Keep an eye on it.

Thanks for the insight. I'll check for oil leakage tomorrow. How soon after your oil change did the problem reappear on your Audi? Was it immediately or over a longer period?

With the Audi, the oil change bought me maybe a week of slightly smoother shifting. But the slipping came back quickly, worse than before. The old gear oil was full of metallic particles, confirming the mechanical wear. Ultimately, I had to get the transfer case rebuilt. Based on your symptoms, I'd strongly suggest getting a mechanic to take a look. If it's defective gears, you're looking at a costly repair.

Thanks for sharing your experience. It's not what I wanted to hear, but better to know. Took it to the workshop today, and they confirmed it. Defective gears in the transfer case. Quoted me 330€ for the repair. Appreciate the help!