535i xdrive 2012 F10 transfer case problems
 

Good afternoon, everyone. Hope all of you are having a better day than me.
The 535i has an oil wear fault code. I was able to remove transfer case fill plug without taking crossmember off or removing electrical plug (straight from the bottom). Thought everything was going well until I removed plug. The car is on stands and not perfect but level. After removing plug about 400ml of fluid came out. From research only a small amount dripping out should be the norm. Fluid is brownish red and thin like transmission fluid. I fear the seal between transfer case and transmission is leaking. Any thoughts or info would be greatly appreciated. Thank you

If so that would be the first I've heard of in a F series. Well at this point if that's your assumption the only thing to do is remove it and check it out. I'd replace it either way if you pull it out. I'd just replace the fluid and check later. 400ML is not that much and could be you're not really leveled. Is it original fluid or it's been changed before.

I'm in the lines of the level, but it's not perfect. Transfer case fill volume should be 1L=1000ml, so when you expect a small stream or drip and you get 400ml. I have to disagree, that is way too much over fill level. No way someone could put that much in fill plug without tilting transfer case. BMW did away with drain plug and only has fill plug. You can't always take what you read as 100%. Just asking questions to see if I have missed something. Thank you

What I'm saying is that you can't be certain the fluid was serviced correctly before you owned the vehicle. It may have even been filled while supported on two stands instead of four, which means the vehicle wouldn't have been level. In that situation, the previous owner could easily have overfilled it during the fill process. That's why I asked whether it had been changed before and suggested performing the service as-is so you can establish a proper baseline and know what you're actually working with. Otherwise, the only way to truly confirm your theory is to drop the unit and inspect it.

Also, an extra 400 ml isn't a significant amount of overfill for a transfer case, and regardless of whether it has a drain plug or not, the correct fill procedure remains the same.

I wish I knew the history of the car. My problem is It's a friend's car. Trying help out, I have a F10 also but it's not xdrive. I have learned a lot just by working through some problems. I'm by no means an expert on cars. I have multiskilled maintenance background, electrical, electronics, programming controls and robots over 40 years. Actual retired from BMW in Greer, SC. I worked in body shop as SSB/ESA. Only manufactured Z3 and Z4 in early years, now only X series.
You are correct about past owners of cars. No way to confirm maintenance unless through dealership. The problem with this car it has a rebuilt title from frontend damage. No way to confirm how significant.
The problem I have with possible over fill is the pressure it may have built up leading to damage. I reinstalled plug. The car is on jack stands, I'm going to run car for 45 to 60 min. Then check to see if any more fluid comes out. I will check level in transmission before doing so.
Thank you for all your input. please if you have any more suggestions, I would like to hear them. Didn't mean to come off as a smart ass. I'm former Marine, we all have a little of that in us.