I used one of those 500 ml hand fluid extractors from amazon and I bought one with the flexible hose. It also came with 2 stiffer hoses but I did not use those. The flexible is the way to go especially if not removing the brace. The biggest issue and I've seen others say is it's not as easy as sliding the hose in. The channel to get the hose down to suck all the fluid out is narrow and seems to have a catch point. took me a bit to finagle it but after the first time I could get it to work easier the next time I inserted it.
I also had bought a new Foxwell NT510 off EBAY a few months ago when they were on sale. It was pretty easy and straight forward to use.
I was able to get 550 mls of dark fluid out. Seems about on par to what I've seen others extract.
I bought the fluid and new drain plug from FCP euro.
I also bought one of those special wrenches off the ECS tuning store EBAY page. It does all the diffs and transfer case plugs. It also is how you can do this easily without removing the brace while it was on sale. https://www.ebay.com/itm/234530015066
If you have any mechanical ability at all and can get your hands on a scanner to open the valve don't spend $500 bucks to get this done at a shop. Like I said it took me around an hour to do. If you can get someone to do it for like $250 to $300 I can see that since you have to buy some tools and a scanner so you could just have someone do it. I think I have under $200 bucks into it with tools, and fluid. But now I have the tools to do this whenever I want.
I do plan on doing the front and rear diffs soon.
"Edit" 4/24/26
I changed the Front differential fluid yesterday. 29,170 miles. 500ml was what drained out and I put 600 mls per what I've read and seen for the M50i using Redline 75/85. The drain plug tool I used for the transfer case barely worked for the up high fill plug. I would suggest you have a backup socket in case you can't get it to fit. The allen head is pinned on the wrench and should use a set screw that you can adjust the length in and out, but it doesn't.
I also did not replace the bolts for the drop-down reinforcement plate that FCP euro says are one time use. I've seen many that don't replace and I don't see any issue with using the same bolts again. If I do it again, I might replace then but I'm not doing it every time. They aren't cheap.
I was going to do the rear diff as well, but the M50 has fins and the tool wouldn't work so I have to buy an allen socket for that. My main concern has been the front diff and transfer case though so those are now done for a bit.
