S8 Transfer Case Issues: Grinding and Gear Slippage Fix

As someone with some repair experience, I dealt with nearly identical symptoms on my A8 from around the same period. The grinding noise and rough shifts were clear signs of gear wear in the transfer case. Initially thought it was just transfer fluid issues, but after inspection, the workshop found defective gears in the transfer case causing the problems. The gear grinding got worse over time, especially during acceleration, just like your situation. The complete repair involved replacing worn components in the transfer case assembly and doing a full transfer fluid change. Total cost was 330 Euro, but it completely resolved the gear grinding and restored smooth operation. To help diagnose your specific case more accurately, could you share: Build year of your S8, Current transfer fluid service history, When the symptoms first appeared, Whether the oil leakage warning has ever shown up, If the grinding sound changes with temperature Catching transfer case issues early typically prevents more extensive damage, so good you are looking into this now.

Thanks for your input. My S8 has now done 146920 KM and had its last major service about 8000 KM ago. Based on your repair experience, I am concerned about potential mechanical wear in the transfer case. During the last service they did check the transfer fluid and found no issues, but the grinding sound has developed since then. The symptoms seem to match what you described, especially the gear wear getting worse during hard acceleration. Will have the workshop do a thorough inspection of the transfer case assembly next week to catch any problems early.

Good to hear back about your S8. The transfer case symptoms you are experiencing now sound very similar to how mine progressed. Even though your transfer fluid checked out fine during the service, mechanical wear can develop relatively quickly, especially after 145000km. The increasing grinding noise during acceleration is a classic sign of progressive gear wear in the transfer case assembly. In my case, the transfer fluid also looked acceptable initially, but the internal mechanical wear was already present. When my workshop did the inspection, they found significant wear patterns on specific gears within the transfer case, this explained why the grinding got worse under load. The fact that your symptoms developed after the last service suggests similar wear progression. Since having the repair done with new components and fresh transfer fluid, my transfer case has been running smoothly for over 50000km with no sign of the previous issues. The early inspection definitely helped prevent more extensive damage and higher repair costs. Make sure the workshop thoroughly checks for any oil leakage around the transfer case seals during the inspection, as this can accelerate wear if present. Keep us updated on what they find.

Thanks everyone for the detailed feedback. The car is now at 146920km and had its last major service around 8000km ago. Based on your repair experiences, I am definitely concerned about mechanical wear in the transfer case. While they checked the transfer fluid during the last service and found no issues, the gear grinding sound has developed since then. The symptoms match what you described, particularly how the gear wear becomes more noticeable during hard acceleration. I have scheduled a thorough inspection of the transfer case assembly for next week. Better to catch any oil wear or mechanical issues early before they lead to more extensive damage. Will keep monitoring the grinding sounds and gear slipping until then. The workshop confirmed they will do a complete check of the transfer case including looking for any oil leakage around the seals. Once they complete the inspection and diagnose the exact issue, I can decide whether just an oil change will suffice or if the transfer case needs more extensive repair work. Thanks again for helping me understand what to look out for.