Refilling transfer case
Thread Starter
Newbie
Joined: Oct 2025
Posts: 11
Likes: 2
From: Rhode Island
2019 Mercedes C43 AMG
Refilling transfer case
I drained the transfer case in my 2019 c43. I replaced the overflow tube but left the drain plug out and refilled through the fill plug. I added 236.15 fluid into the fill hole until it started to trickle out the fill hole, but nothing had come out of the overflow tube/drain plug yet. What concerns me is that I had only added between three and four tenths of a liter at that point- about half of what I expected to put in. On the other hand, I don't think .6 liters of old fluid drained out either! Obviously I couldn't add any more because it was trickling out the fill hole as I added! Why did it seem full when I hadn't put in nearly the amount that I expected to??
Thanks-
Brian
Thanks-
Brian
Thread Starter
Newbie
Joined: Oct 2025
Posts: 11
Likes: 2
From: Rhode Island
2019 Mercedes C43 AMG
There is a little vertical tube, maybe a little over an inch long. It clicks into the drain hole above the drain plug. When you add fluid through the fill hole, that tube will allow youto fill the transfer case sump until it reaches the top of the tube and then excess will drain out. Theoretically, this lets you fill the transfer case with the right amount of fluid. Then you replace the drain plug. I had added fluid into fill hole until no more could fit, but still not coming out of drain tube. Weird.
Thread Starter
Newbie
Joined: Oct 2025
Posts: 11
Likes: 2
From: Rhode Island
2019 Mercedes C43 AMG
MBWorld Fanatic!
Joined: Oct 2019
Posts: 5,151
Likes: 1,765
From: Colorado
G550
I'm still confused -- you remove the drain plug to let out the old fluid, and then add new fluid through the fill plug until it flows out the drain plug? Is this what the WIS procedure prescribes?
Thread Starter
Newbie
Joined: Oct 2025
Posts: 11
Likes: 2
From: Rhode Island
2019 Mercedes C43 AMG
Pretty simple but hard to describe. The little overflow pipe fits at the top of the drain hole. So for fluid to drain out it would have to be at a depth greater than the height of the pipe. That means that to drain the transfer case completely, you would need a little wire hook to pull the Overflow pipe out. It comes out pretty easily, then all the fluid can drain out. That little overflow pipe is then clicked back into place before you fill the transfer case.
MBWorld Fanatic!
Joined: Oct 2019
Posts: 5,151
Likes: 1,765
From: Colorado
G550
Pretty simple but hard to describe. The little overflow pipe fits at the top of the drain hole. So for fluid to drain out it would have to be at a depth greater than the height of the pipe. That means that to drain the transfer case completely, you would need a little wire hook to pull the Overflow pipe out. It comes out pretty easily, then all the fluid can drain out. That little overflow pipe is then clicked back into place before you fill the transfer case.
Trending Topics
Thread Starter
Newbie
Joined: Oct 2025
Posts: 11
Likes: 2
From: Rhode Island
2019 Mercedes C43 AMG
Filling transfer case on 2019 c43
Curiosity got the best of me, so I had to lookup the WIS procedure. Not much in illustrations -- just where the xfer case is, and where the drain/fill plugs are. Fill capacity says 0.65 liters, so you aren't too far off if there was any residual that didn't drain. Did you search for any YT videos?
MB World Stories
The Best of Mercedes & AMG
Manual Mercedes? 6 Times Sindelfingen Let Drivers Have All The Fun
Verdad Gallardo
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Verdad Gallardo
8 Classic Boxy Mercedes Designs That Have Aged Like Fine Wine
Verdad Gallardo
Flawlessly Restored Mercedes 190E Evo II Heads to Auction
Verdad Gallardo
Electric Mercedes C-Class Unveiled: 11 Things You Need to Know
Verdad Gallardo
Mercedes EQS Gets A Major Update: Everything You Need to Know
Verdad Gallardo
5 Underrated Mercedes-Benz Models That Don't Get the Love They Deserve
Verdad Gallardo
Mercedes 300D Has Pushed Well Past 1 Million Miles and It Ain't Stopping
Verdad Gallardo
10 Most Reliable Mercedes-Benz Models You Can Buy Used
Verdad Gallardo
Junior Member
Joined: Jul 2025
Posts: 48
Likes: 8
2020 AMG C 43
I replaced the overflow tube but left the drain plug out and refilled through the fill plug.
