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Done.... The transfer case and both differentials changed (along with the oil and filter) today. 93k on the clock. All driveline fluids were changed at 50k from tip to tail once before. Some observations....
1) WATCH those videos further up this thread. Pay close attention to how he gets the (a) rear differential drain plug out, and (b) the front drain plug out. They are tricky due to (a) the exhaust pipe being in the way, and (b) the oil pan. What you will need:
For the front - it's a Torx 50. You want the wrench, not a socket to a wrench. Not enough room for a wrench/socket set up. But a basic dedicated Torx wrench will fit in the space. You'll (very likely) want a cheater bar to give yourself some leverage. Mine were on there super tight, hard to break loose.
For the rear - it's a 14 Allen wrench. And yet again, not enough room for a socket+wrench on the drain plug. What I had to do - I bought an Allen socket set that included the #14 size. I have a 14 crescent wrench as well. I placed the crescent wrench over the Allen bit and slid that into the bolt, giving it about a ¼ of inch bite into the bolt, then a cheater bar over the crescent wrench and pulled like my life depended on it. If you have a floor jack handy, you could possibly use it to leverage up the wrench. Mine was on there like God himself installed it.
The transfer case is an 8 Allen, very easy to do. May have to remove the plastic shield a bit to get a wrench up to the fill plug. Drain plug is right there, easy access.
Findings at 43k miles on the fluids.
Front Differential: The old looked just as good as the new going in! Seriously, showed 0% sign of wear whatsoever.
Rear Differential: The same as the front!!! Maybe a minor shade darker than light tan in color, but certainly not showing any real signs of strain or stress. I was expecting the rear to be dark brown since it's a RWD bias setup on a very heavy car. But no.... Looked damn near perfect at 43k miles of usage!!!
Transfer Case: This was odd.... The fluid that came out was a red as any new transmission fluid that you've seen. Showed no signs of real wear whatsoever. However, it was red. The new fluid that was put in...was dark tan, not red. I'm thinking either the shop at 50k made a mistake (MB is known for using transmission fluid in their transfer cases), or MB has changed up the transfer case fluid since we had the 50k service done back in 2022. My part number / fluid is the correct version per every manual I've seen and does match the bottle in the video. I'm thinking the shop made a mistake, as we did the transmission fluid at that time as well. But considering 0% signs of wear on the fluid after 43k miles of mostly top/go errands, I have no concerns of damage done.
Amounts: I had 4 bottles total for the differentials, and two bottles total for the transfer case. I knew I had too much, but was expecting the need to "flush" a bit out of the differentials to clear the contaminants. I think 3 bottles total for the diff's is fine. The 4th is not needed.
The transfer case took in a little over a bottle, perhaps a 1 ½. Buying two bottles for that service was a wise move.
End of the day, pretty easy for a first time DIY on this car. The hardest part was the rear diff drain plug and how tight it is against the exhaust pipe. Made a trip to Harbor Freight for a 14 Allen socket and some MacGyvering with a crescent wrench and cheater bar to get mine to bust loose. But once it did, it was easy as pie after that.
I did not change the drain/fill plugs. I reused the ones there. Honestly, they fit so damn tight, and I snugged them down pretty hard, that I doubt any of them are going to leak. But I'll keep my eye on them and the garage floor for a few days just in case.
I use this, and it is wonderful!!! Can't recommend it enough. Made easy easy easy work of filling up the components.
My conclusion: I. Am. Impressed!!!! Seriously, impressed. I can't believe none of those fluids showed any signs of wear after 43k miles. No glitter, no burnt smell, hardly any discoloration. I have to give it to Mercedes Benz on that one. I have -0% concerns over the integrity of the driveline components after nearly 6 years and 93k miles. Perhaps they should ask the engineers in the driveline department to take a look at the door switch engineers!! Ha!!
For the front I tapped out my socket Torx 50 stud as the video described for the rear diff. I was able to tap the torx stud back into the socket when I was done.
I purchase an expensive fluid pump too but from Vevor. However, I ordered this
too for the hell of it and never even opened the Vevor box.
I also changed my oil, I had a kit from the dealer sitting around for a couple of months now. It is terrible I had to get on my back and change the oil on a MB, I haven't done so in over 20yrs! I usually use a fluid extractor through the dipstick tube. I initially poured 8.25Qts of oil in which got me to the Min. mark on the Engine Oil Level measurement on the dash. I added 1 full quart to get to the "Max" level.
What is not mentioned is if you are using jacks and jack stands, getting that steel skid plate on and off can be a PITA! My arms felt like I changed 15 recessed light bulbs, without a ladder!
Some random pics I took below. Might as well change the oil too while ur there, or might as well change your front Diff fluid if you're changing your oil. Not looking too bad coming out. The GLS580 has alot of AMG letters stamped all over the engine bay and now I see underneath as well.
Originally Posted by nc211
Done.... The transfer case and both differentials changed (along with the oil and filter) today. 93k on the clock. All driveline fluids were changed at 50k from tip to tail once before. Some observations....
1) WATCH those videos further up this thread. Pay close attention to how he gets the (a) rear differential drain plug out, and (b) the front drain plug out. They are tricky due to (a) the exhaust pipe being in the way, and (b) the oil pan. What you will need:
For the front - it's a Torx 50. You want the wrench, not a socket to a wrench. Not enough room for a wrench/socket set up. But a basic dedicated Torx wrench will fit in the space. You'll (very likely) want a cheater bar to give yourself some leverage. Mine were on there super tight, hard to break loose.
For the rear - it's a 14 Allen wrench. And yet again, not enough room for a socket+wrench on the drain plug. What I had to do - I bought an Allen socket set that included the #14 size. I have a 14 crescent wrench as well. I placed the crescent wrench over the Allen bit and slid that into the bolt, giving it about a ¼ of inch bite into the bolt, then a cheater bar over the crescent wrench and pulled like my life depended on it. If you have a floor jack handy, you could possibly use it to leverage up the wrench. Mine was on there like God himself installed it.
The transfer case is an 8 Allen, very easy to do. May have to remove the plastic shield a bit to get a wrench up to the fill plug. Drain plug is right there, easy access.
Findings at 43k miles on the fluids.
Front Differential: The old looked just as good as the new going in! Seriously, showed 0% sign of wear whatsoever.
Rear Differential: The same as the front!!! Maybe a minor shade darker than light tan in color, but certainly not showing any real signs of strain or stress. I was expecting the rear to be dark brown since it's a RWD bias setup on a very heavy car. But no.... Looked damn near perfect at 43k miles of usage!!!
Transfer Case: This was odd.... The fluid that came out was a red as any new transmission fluid that you've seen. Showed no signs of real wear whatsoever. However, it was red. The new fluid that was put in...was dark tan, not red. I'm thinking either the shop at 50k made a mistake (MB is known for using transmission fluid in their transfer cases), or MB has changed up the transfer case fluid since we had the 50k service done back in 2022. My part number / fluid is the correct version per every manual I've seen and does match the bottle in the video. I'm thinking the shop made a mistake, as we did the transmission fluid at that time as well. But considering 0% signs of wear on the fluid after 43k miles of mostly top/go errands, I have no concerns of damage done.
Amounts: I had 4 bottles total for the differentials, and two bottles total for the transfer case. I knew I had too much, but was expecting the need to "flush" a bit out of the differentials to clear the contaminants. I think 3 bottles total for the diff's is fine. The 4th is not needed.
The transfer case took in a little over a bottle, perhaps a 1 ½. Buying two bottles for that service was a wise move.
End of the day, pretty easy for a first time DIY on this car. The hardest part was the rear diff drain plug and how tight it is against the exhaust pipe. Made a trip to Harbor Freight for a 14 Allen socket and some MacGyvering with a crescent wrench and cheater bar to get mine to bust loose. But once it did, it was easy as pie after that.
I did not change the drain/fill plugs. I reused the ones there. Honestly, they fit so damn tight, and I snugged them down pretty hard, that I doubt any of them are going to leak. But I'll keep my eye on them and the garage floor for a few days just in case.
My conclusion: I. Am. Impressed!!!! Seriously, impressed. I can't believe none of those fluids showed any signs of wear after 43k miles. No glitter, no burnt smell, hardly any discoloration. I have to give it to Mercedes Benz on that one. I have -0% concerns over the integrity of the driveline components after nearly 6 years and 93k miles. Perhaps they should ask the engineers in the driveline department to take a look at the door switch engineers!! Ha!!
As my best says - “only you, would buy a Benz and put it on blocks”! That all started with an old Lexus LS400 I had 20 years ago. I enjoy it though, but won’t argue against the fact that I’m getting a bit too old for the floor. I don’t bounce up on my feet quite as fast, and usually have to finish it off with a few Advil!
I tried to unseat the 14 Allen from its socket for the rear, but wouldn’t budge. Thankfully the matching 14 crescent was able to do the job via the exposed part of the socket.
Photo was when I was doing the transfer case. Leaned it to the driver’s side, access via the passenger side.
Only time I’ve ever used “off road” mode too! Helps with lifting it up a couple more inches for my fat as$ to get under it!
Gave it a bath today to get all of the dried road salt off it (tons)! Which reminds me - I saw not a spec of flash rust anywhere underneath. Thing still looks brand new under there from front to back. Pretty impressive! Even the original brake rotor hats still look new!
The topic of lubricants is extraordinarily complex, and my level of knowledge is just beyond knowing how little I know. However, my understanding is that lubricants are subjected to high shear stresses that break down their polymer molecules. Engine oil turns black due to combustion contaminents and heat. But when it appears this way after only 500 miles, it doesn't mean it's already wasted. Gearbox lubricants exist in sealed environments, usually at lower temperatures. Judging the condition of a gearbox lubricant after 50K miles just by its color or its observable viscosity is not a reliable measure of its integrity and suitability for continued use as it could be a molecular train wreck. Changing gearbox fluids at manufacturer recommended intervals (or sooner) is never a waste of time and money.
I'm bringing this back up to the top, as I have a problem. I have a humming noise on parking lot turns and under moderate acceleration when coming out of a turn. Sounds like it's the rear diff or transfer case (leaning more towards transfer case). The transfer case IS limited slip on the standard GLS. I'm curious if anyone can confirm that part # 000989340209 is the correct fluid for the 2020 GLS transfer case, and does the bottle look like this picture?
I am also curious if there a limited slip additive that should accompany the fluid? And should it be gold in color, or red like transmission fluid (which has mostly been the case for MB 4Matics).
I'm bringing this back up to the top, as I have a problem. I have a humming noise on parking lot turns and under moderate acceleration when coming out of a turn. Sounds like it's the rear diff or transfer case (leaning more towards transfer case). The transfer case IS limited slip on the standard GLS. I'm curious if anyone can confirm that part # 000989340209 is the correct fluid for the 2020 GLS transfer case, and does the bottle look like this picture?
I am also curious if there a limited slip additive that should accompany the fluid? And should it be gold in color, or red like transmission fluid (which has mostly been the case for MB 4Matics).
I’m having the same issue. Please let me know if you’ve confirmed this and if this fixes it.
Regarding that noise, I just realized that sound was gone when I left the garage at work last week.
Originally Posted by nc211
I'm bringing this back up to the top, as I have a problem. I have a humming noise on parking lot turns and under moderate acceleration when coming out of a turn. Sounds like it's the rear diff or transfer case (leaning more towards transfer case). The transfer case IS limited slip on the standard GLS. I'm curious if anyone can confirm that part # 000989340209 is the correct fluid for the 2020 GLS transfer case, and does the bottle look like this picture?
I am also curious if there a limited slip additive that should accompany the fluid? And should it be gold in color, or red like transmission fluid (which has mostly been the case for MB 4Matics).
Everything I’ve read, and talked with the dealer again in great detail, says that all of these fluids are indeed the correct fluids to use for the differentials and the transfer case. So I have no idea what is causing the noise. My gut is telling me that perhaps the brake pads are harmonizing on the moisture glade when turning, as the car uses the brakes to simulate a limited slip differential on the rears. My brakes are still the originals. I am going to put in the Liqui Moly additive as soon as I can find the time to see if that does anything. If it doesn’t, then I’m leaning even more towards the brakes.
Hi, I have same problem on my GLC Coupe after I replaced factory oil by Fuchs Titan Sintopoid FE 75W-85 which has 235.7 and 235.74 aprovals by MB for front differential, but it is just RECOMMENDED for rear differential by Fuchs (239.71). One forum member had same problem after using Fuchs oil and solved it by replacing it with genuine oil 239.71. Some members let it work and noise disappeared. Do you have this problem after replacing oil (which oil) or with genuine factory oil?
Installed the Liqui Moly MoS2 additive and it absolutely took out the noise in the rear. I see why some dealers use it.
I think what I hear now as we come out of a turn with mild acceleration are just the tires, which are getting close to needing replacement as well.
If you do it, wear latex gloves. It's messy. It's like a liquified graphite. Very thin, black as midnight, and a ton of fun to get out from under your finger nails.
It doesn't really matter as it mixes with the gear oil. I just popped the fill plugs off and squeezed in the tube, then put the plug back in.
I do still hear it a little, but I don't think it's just the differential. It reminds me of my old W212 when the transmission mount started to signal that it was compressed down too much and would transmit a sound throughout the chassis under very specific / gentle conditions. When I'm done with my 100k refresh, which will include a new transmission mount, brakes, and tires, I'll see if it's still there. The LM absolutely made a nice difference though, no doubt.
I'm almost positive it's the transmission mount making the noise. I think when turning, the transmission is shifting on its mount. Why I say this - the noise changes as the gears change too. Noticed it today. I think when turning, it's putting more torque on the transmission itself. No logical reason for the noise to change pitch downward as the speed increases then goes away when straightening out. If it were the diff, I'd think the sound would increase in octave into a whine, not decrease into a groan right when the transmission starts to down shift to the next gear. The transmission mount at 6 years and 93k miles would make perfect sense to be wearing out. My W212's mount was shot at 50kish and roughly 5 years and would send a groan and slight vibration whenever it would shift from 4th to 5th under gentle load.
I'm throwing my hands up on this noise, which I can now feel in the arm handles of the center console of the car as a faint vibration. I swear on everything I know about cars - it sounds EXACTLY like a problem with a limited slip differential. Yet, everyone swears it's not a LS differential in the GLS450. But it sounds, and acts, exactly like that. Exactly.
Turn the car at parking lot speeds, it hums. Harder you turn it, the harder it hums, then as it straightens out, it goes away, even as you accelerate up to speed. And it goes away quickly. Not present at cruising speed whatsoever, smooth as glass. Not even present at speed when making turns. It's just when you're at parking lot speeds and making turns. It just hums/groans. The fact that it goes away at speed, does not suggest a bearing. It's not a whine that increase in pitch with speed. It's a groan that is its loudest at slow speeds and sharp turns. To me, that 100% suggests and feels exactly like a LS clutch plate slipping. My shop, the dealership, and that confusing as all hell MB fluid website all swear what I put in the differentials is exactly right (showed them the pictures of the bottles).
But I am left wondering why the old transfer case fluid was red as fresh transmission fluid coming out with the same consistency, yet the bottle that went in was golden honey looking oil. Yes, meets the stated MB 239.41 spec for my car. But it says "gear oil". What gear oil is red like transmission fluid? The bottle also says nothing about a Limited Slip, which the transfer case indeed DOES have.
Either way, it's heading in to the shop on Friday for the guys to figure out. I give up. If I were to make a bet, I would say either (1) the MB gear oil for the transfer case is wrong or (2) the rear diff on a staggered setup GLS is indeed a limited slip differential. I think the trans mount is getting close, but what are the odds that this all started when I changed these fluids? Something is off with these fluids, is my bet. And the more I talk about it, the more I think it's the transfer case. Correct me if I'm wrong here guys, many far more experienced than I with this brand - but for YEARS, MB used transmission fluid for the transfer case and not "gear oil".
No, the differential does not have a LS fluid or additive. That was one of the initial errors in fluid understanding from the dealership, which initially presented me with the Castrol Transmax Limited Slip 75w-140 (MB 235.61) fluid. But that ended up being meant for the AMG variant of the GLS. I did not buy it.
No, the differential does not have a LS fluid or additive. That was one of the initial errors in fluid understanding from the dealership, which initially presented me with the Castrol Transmax Limited Slip 75w-140 (MB 235.61) fluid. But that ended up being meant for the AMG variant of the GLS. I did not buy it.
I'm wondering if you have an alignment problem, or other tire issue. Scrub can make noises, as can the Ackermann effect.
Did they use Chassis Ears to pinpoint the noise"
I never add additives to lubricant any more, since the chemistry has become so specific. 20 years ago, I did.
Hope you/they don't rule out any possibilities and that you get satisfaction.
Alignment is straight, no uneven wear on the rear tires either with about 50% of the tread left.
I'm thinking I just have the wrong fluids somewhere. I went back to those YouTube videos I posted further up in this thread. I paused on the fluid he's using - Redline 75w-85 FOR LIMITED SLIP. Me adding the Liqui Moly would make the problem worse, as it's specifically not for Limited Slip.
I pulled up the Fuchs site on the bottle I used, and have some questions on it. It too says it can be used for limited slip. But Mercedes Benz tells me I do not have a limited slip rear differential. So. Something is wrong here. Lost in the confusion. Time to throw in the towel. GD Mercedes and their overly complicated BS.
It's really annoying how little the dealer service departments know about the cars they service, but I guess they rely on the manufacturers who know even less. I'm about to change the differential and xfer case fluids in my X7, because the "lifetime" fluids that are factory fills are anything but. Worse, BMW plays whack-a-mole with the fluid specs, so no one seems to know what fluid applies to which model at any time. I'm convinced its more important to change the fluid frequently than to worry about whether you've used 75W-90 instead of 75W-80. I'm planning to put Redline LS 75W-85 in both diffs and do it again every 15K miles.
It's really annoying how little the dealer service departments know about the cars they service, but I guess they rely on the manufacturers who know even less. I'm about to change the differential and xfer case fluids in my X7, because the "lifetime" fluids that are factory fills are anything but. Worse, BMW plays whack-a-mole with the fluid specs, so no one seems to know what fluid applies to which model at any time. I'm convinced its more important to change the fluid frequently than to worry about whether you've used 75W-90 instead of 75W-80. I'm planning to put Redline LS 75W-85 in both diffs and do it again every 15K miles.
Get a fluid sample. Describe your symptoms to Blackstone Labs and ask for advice. They'll answer.
Before it goes to the shop tomorrow, I’m changing the fluid one more time. But this time, no more of this confusing and overly expensive Mercedes garbage, and going with what has treated me exceptionally well for over 25 years across many different brands. Will be putting in Mobile 1 GL5 75w-90 LS to see if that fixes it. I am employing the life-learned lesson that has NEVER let me down - “A million rednecks can’t be wrong”.
It’s a f’n differential!! It’s not a jet turbine. It should not be this damn confusing.
I will say, if my rear differential is toast at 95k miles of an exceptionally well maintained grocery getter - then this puppy is going to become a VW Atlas SEL R faster than a fart in the wind, and MB will never see my driveway again. Even my shop guys are saying there is no way the differential should be going bad on our car.
FYI I recently did all my fluids 1500kms ago in my 2020 GLS 580 with 80000kms, (50k miles). I used MB brand trans fluid and MB brand transfer case fluid and Redline 75W85 for the front and rear diff. No issues before the change or after the change. The fluids I removed did not look excessively dark.
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
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