BMW 8 Series AWD Issues, Transfer Case Problems?

Hi there! I've got some experience with BMWs and had a similar issue with my 2020 BMW 6 Series last year. I'm not a pro mechanic but I'd say I have some experience working on cars. The symptoms you're describing sound exactly like what I dealt with. My car was also showing multiple warning lights and had rough shifting. Initially thought it was the transfer case, but turned out it was actually related to a faulty ABS module that was causing these cascading issues with the drivetrain. Luckily, it was covered under warranty, so I didn't have to pay anything. My dealer ran a full diagnostic and found that the ABS system was sending incorrect signals, which made the all-wheel drive system go crazy. Before I can help more specifically, what's your exact 8 Series model (840i, M850i)? Also, has your car had any recent work done, or did these issues start suddenly? This info would help narrow things down. I'd definitely recommend getting it checked ASAP since these symptoms could potentially lead to more serious problems if left unchecked.

Appreciate the detailed response! I've got an 840i with 167134 KM on the clock. Just had my routine service done last month. The issues started popping up gradually over the past few weeks. Started with occasional warning lights, but now it's getting more frequent. Based on your experience, I'll definitely have them check the ABS module. Makes sense that it could mess with other systems since everything's so interconnected in these cars. Thanks for the heads up, I'll book it in for a proper diagnosis soon before it turns into something worse.

Hey again! Thanks for providing those extra details about your 840i. Now that you mention the gradual onset of issues after your service, it actually reminds me even more of what happened with my car. You know what's interesting, after my ABS module issue was fixed, I remembered there were actually some subtle warning signs I'd missed. Started with unusual warning light flashes here and there, just like you're experiencing. Initially, I brushed them off thinking it was just electrical gremlins. With the mileage you're mentioning, I'd actually be curious if they checked your wheel speed sensors during that last service. In my case, it turned out the ABS module wasn't the only culprit, one of my wheel speed sensors was also acting up, which was messing with both the ABS and the transfer case signals. These sensors can get pretty dirty or worn over time, especially at higher mileages. Keep me posted on what your dealer finds. Would be really interesting to see if it's similar to what I experienced. And definitely don't wait too long, I learned that lesson the hard way when I tried to "drive through" the initial warning signs!

Thanks so much for the additional info about the wheel speed sensors! That's actually super helpful, I hadn't even considered that could be part of the problem. Come to think of it, I don't remember them specifically mentioning checking those during my last service. Makes total sense that dirty sensors could trigger all these issues, especially given how many miles I've put on the car. I've actually just booked an appointment for next week at my dealer. Will definitely have them take a look at both the ABS module and the wheel speed sensors. Really appreciate you sharing your experience, it's given me a much better idea of what to discuss with the technicians. I'll make sure to update this thread once I get the diagnosis and fix. Thanks again for all the helpful advice!