What Transfer case fluid does this vehicle use?

Looks like this vehicle takes gear oil in the transfer case so I attached the info below on this from the manual.

However, I am not sure if this vehicle has a drain plug or not as I am not finding a process from the manual on how to change the fluid.

This is typical for Mercedes because they don't put a lot of stuff out on this type of stuff.

Let us know what other info you need on this. Thanks

I am a bit confused on what this means in the picture. But I found someone in the forum mentioning this...there are 2 differentials? one rear and one in front? plus the transfer case? I thought the transfer case behind the transmission is the same as the front differential...
This is what they said:
(I did it on my X164 and plan on doing the same on 2015 GL 550 as well.

Transfer case uses the same Trans fluid.
Front\Rear Diff uses 75W90 Oil. )
Isn't the part that has the chain the transfer case?

The only transfer case that takes ATF is BB00.40-P-0236-12A.

So if you have this transfer case then that is correct. However, I am attaching pictures of the front and rear axle plus the part number of the transfer case that the manual has for this vehicle.

It says the front and rear axles take 75w-85 and the transfer case takes what I attached before with the exception of that unit number above in this post which takes ATF.

So there are 2 types of transfer cases. How can i tell which i have?

It does not say so that is going to be by the VIN and sales codes or a stamping on the side of the unit.

Do you know if this has an off-road package on it or not?

I will check if there Are any stamps on transfer vase. No off-road package, just adjustable suspension. As in sport vs normal mode.

Okay. That appears to be the 750.65 transfer case which would be ATF.

Hopefully you find some stampings that will support either of these numbers.

Have you drained the fluid? We should be able to tell pretty easily by what is in it.

No not yet. Waiting on the transfer case chain and wanted to get everything including fluid so i won't be lazy putting everything together. I will check it today.

Sounds good. Let us know what you find because it would be nice to confirm which fluid it is.

Thanks

I go down to see the transfer case but there are no numbers anywhere on it. But i see the drain and fill round plugs.

And to be clear I am talking about the one that is right behind the transmission which has the driveshafts attached, not the front case which has the axles attached.

Perfect. That is the transfer case and those are the drain and fill plugs. Based on that, I suspect you are correct that this is the unit that takes ATF.

If it were me, I would get both oils and just return the one that it is not when you drain it.

However, based on this info, I am pretty confident that the ATF is what you will use.

Thanks for the follow up.

Yes, I am almost sure as well. how can you tell the difference in oil once drained since both going to be black?

Haha. Good point but you will put it in a pan and swirl it and you should see a red tint to it when it is really thin. Think of it like the ocean. In the shallow portions you can see the floor. The deeper it gets, the darker the water. So, you want to have a real shallow portion and you will see the tint to it. The only time that that does not work is if the fluid is so burned that it looks like motor oil. However, if that were the case you would have bigger issues than just changing the fluid.

What if the chain breaks? Basically it will be a 2wd?

Correct but that chain is not going to break without it being obvious. I have seen these types of transfer cases fail and it puts a hole in the side of the case.

Basically, if there is enough force to break the chain then that chain will put a hole in something else.

Let us know what you find with the fluid.

Oh wow. Thanks

Drained fluid, and it's pretty much dark black. Dropped driveshaft center bearing bolts so i can have room to pull transfer case cover. Wow this chain is loose. They only have one guide, but how can they become so loose? Just from stretching. This is insane.

Do these come with gaskets? Okay, only see a paper-like one on the transfer case cover. Can i use some black silicone?

Yes. Silicone will work.

However, when you drove the vehicle, was there any banging or slapping noise when you were engaging 4WD?

Those chains are normally not that tight. They are like bicycle chains on steroids. They just transfer the power from one side sprocket to the other and when they are under tension, they tighten up.

If you didn't have any slapping or banging when in 4WD then there is nothing wrong with it.

Was there an issue with the system or are you just performing maintenance?

Also, about the fluid, when you drained it, did it run out like ATF or was it really thick and take a while to drain?

Just from the look of that entire set up, it looks just like every other one that takes ATF.

This car is always AWD. There was no noise at all except for when you downshift hard say to pass someone you will hear a chain skip, similar to one on a bicycle. Does it for couple of seconds and goes away. No lights on the dash. No, the fluid drained quickly not thick.

Okay. That helps. Then yes it looks like that chain is slapping the case. It is unlikely to be slipping because those think chains will damage the teeth of the gears and you would see that.

Take a look at the case and surrounding parts and see if there are any witness marks that would be the chain slapping.

If you see nothing, then I suspect the transfer case if just worn out.

That is very common with AWD vehicles and there is no info on rebuilding them.

I am sure you can, but you would have to find parts and then work through it. MB says to replace them.

One thing you need to do before you do anything more than replace the fluid is make sure all four tires are the same size. I don't mean the same size that is stamped on the side. I mean they actually measure the same.

Use a string and wrap it around each tire and make sure they are within a quarter inch of each other circumference wise.

If they are not, they damage the transfer case and the only way to fix that is to replace it.

As for the fluid, if it came out fast then that is ATF. No question.

Yes, the tires are good, they are actually new Michelins. I know with
Awd vehicles tires are a big factor and must be sane tread.

In just checked the teeth on both gears and they are in excellent shape. Rotated the shafts on the transfer case and they are smooth, no signs of a bad bearing. If this was internal and major there would have been a continuous noise if I am not mistaken, but the fact that it only does it once there is a hard slam suggests it's a skip, similar to a bicycle. Once i get the chain I will send you a picture, am almost sure it is stretched.

Yep. So that was the next step. If there are no signs of slapping and the teeth are okay the chain is stretched.

However, that is rare so if you have a chain coming, just lay them on a table to compare them. They should obviously be the same length.

Let us know because that would be interesting to see if this is the issue. Thanks

As i suspected it is stretched and now it has minimal play. Putting fluid tomorrow.

Just filled it out and driven it all good, no noise.

That is great news. Something drastic had to have happened to that because I had only seen a handful of chains stretched and none of them were that thick.

Great find. Clearly you have good instincts. I will remember that for next time.

Thanks again for the updates and the picture.

Yes, i have seen a video of someone doing on a gl450 and assumed it was the same, he also had same finding, i guess it is common issue but if we are too late it would have made a hole in the case like you said.

Interesting. So, if there are more than one then I suspect what happens is the chains are more sensitive to heat. So, if the fluid is not maintained then it gets hot, and that chain will stretch. Heat is the cause of the expanding of any of these chains but since your fluid was black, I suspect that it completes the story because heat is what causes the fluid to turn dark.

Thanks again.

I wasn't aware that older fluid can heat up more? hmm, what about engine timing chains, I hear lots of horror stories on them stretching as well...not enough oil changes? Is that the only possible cause?

When the fluid deteriorates it loses a lot of its properties including the ability to dissipate heat. So that means the unit gets hotter. As the unit gets hotter, the fluid breaks down more and it turns into a cycle.

So, as the unit gets hotter because the fluid is broken down, the metal gets malleable and when it is put under tension, the metal stretches.

Timing chains fail the exact same way. Keep in mind, this is rare, but it does happen enough that we should keep an eye on it.

Other people say that a chain will stretch under heavy loads, but I never bought into that because it doesn't make sense. The load is on the joints and not the turning components like this. In order for them to stretch under load the two mounting points (sprockets) would have to be moving in order to stretch it and they are stationary.

What do you mean by the load is on the joints? But the chain is also turning, and turning quick, so why would it not stretch? If the guide breaks that's a different story.

The connection points all through the drive train. The u joints, input and output shafts, etc.

The chains are turning fast but if centrifugal force were enough to stretch the chain, then all chains would stretch. So even though they are spinning fast they are not going to stretch without something else happening to them.

What I mean by load is pulling a heavy trailer or going up a lot of mountains. This type of load has no effect on timing chains or transfer case chains but is hard on u joints and input shafts.

Oh, Ya that i agree with.