2017 c220d ... Thicker transmission fluid to help with gearbox issue?

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Stevolution

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Mar 22, 2025
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I have a problem with my c220d 2017.
After 10 miles driving it starts to drop from drive into neutral when at standstill.

I’m thinking as the oil gets thinner, the problem presents itself so my question is, do you think I could perhaps put a thicker oil in the gearbox that won’t thin out the same?

I know this sounds like white a hack but I’ve nothing to lose. 3 people have seen the car and only solution seems to be new gearbox and hydraulic system. I understand it’s a band aid approach but I just wondered if any of you guys would have some insight.

The code that comes up is p073e00. When the car is cold it drives flawlessly.
If I leave it in sport it stays in gear although the eml will come on and off intermittently

Thanks guys, it’s my first post
 
With any gearbox, make certain that the fluid is fresh, and the level correct, before diagnosing it.

So, I wouldn’t change to thicker fluid, it’s not going to make much difference, but I would change the fluid to a Mercedes approved fluid, and ensure the proper level as a next step.

I believe your transmission uses a 236.17 - if that’s not right, then please adjust where you search for fluid - but start your fluid search with approved fluids, here:

https://operatingfluids.mercedes-benz.com/sheet/236.17

Additionally - How many Km are on this car? Are you the original owner? Who serviced this? With what fluid?

A bit of history might point to the problem beyond just your shifting symptoms. To be prepared, if it works properly in sport mode, that points to a control system (valve body and/or sensor) problem.

On a late model MB, the conductor plate (sensors and solenoids control unit) is an easy swap mechanically - but it is a “theft relevant” part, meaning that you need the full up MB software to program that conductor plate to your VIN to allow it to work correctly. You may need a new gearbox, but more than likely, it’s the conductor plate, or one of the solenoids controlled by the plate.

Start with the fluid change and level check.
 
Only if it's the same spec. Also when was the last fluid change? if it hasn't been changed it may be sheared down a bit too much.

I know that some atf's can be thinner or thicker than others but still be allowed. Toyota ws is much thinner than aisin ws for example and it was likely for fuel economy. In your case i don't really think it could work but may help. I imagine you're not in north america since that c220d was never sold here.

Google says you have the 9 speed and that it needs 236.17 and i would suggest combing through them and look for one with the highest kv100. After looking up a few 236.17 pds's it seems to have a super low viscosity of 4.1 and one called Dyade seems to be thicker at 4.8 kv100 but i don't know if you can get that thought it doesn't have to be that one. Look for ones you can get and check the kv100. Try the thickest one and maybe do two two drain and fills. If that doesn't work then I would look into having the pressure sensors replaced. They may be reading low but I don't think so.
 
Kira said:
After assuring correct fluid at the correct level, the P073E00 code cited in the part listing would tell the whole story, no?
Click to expand...
No.

You can get a code for the solenoid, but when you meg out the solenoid, it’s fine.

The conductor plate controls the solenoid - and a bad conductor plate will throw that code because the plate resistance is wrong - which sets the solenoid code.

Codes never tell the whole story - they are a starting point.

The computer sees a value (voltage, operating time, whatever) that is wrong and sets a code, but the part or sensor that is out of range is often not the cause. E.G. a EGR code on a car may not be the EGR valve - it may just be the vacuum line to the valve that is cracked.

Hack mechanics fire up the parts cannon (often at customer expense) based on codes. Real mechanics read the codes and then start troubleshooting.
 
Thank you all for replying so quick and I’m sorry this post is so dialogue rich.

1 year ago the gearbox was flushed

3 months ago it started playing up so we booked into a mechanic. 2 months later they had dropped the sump, then told us they can send the gearbox to their specialist for £1500. We just wanted the car back at this stage to explore other avenues. They told me I stopped driving it on time as there was a small amount of iron filings in the sump. I asked them to put new mercedes oil back in for 2 reasons, because oil was contaminated and I didn’t know if part of the problem could have been wrong oil or low filled) when I got it back I drove it around 10 miles and it drove perfect, I have to say, I started to get quite excited, and then it did its thing again. It does seem to drive longer now, usually 2 miles would be enough, now it will do at least 8 miles.

We then took it to a mercedes specialist that had been recommended to me, they wanted to do a software update first (this failed or didn’t cure). They dropped the sump and could see the oil was clean with no fragments, (It had done around 40 miles since it was changed) I’d told them about the previous mechanic finding “small amount of metal” and they said although it seems the hydraulic unit is at fault, they would rather not do it because is the shaving findings, they sent me to a gearbox specialist.

The car is worth £11,000 I’m running out of options but i really don’t want to have to spend £4-5000 on this.

There is company’s in uk that you can send your tcu to and they will swap out the pressure plate, for around £200.

There is a detailed 9g tear down on youtube, I’m so tempted to have a go at removing it and sending it away for repair. I have a detailing workshop but I don’t have a ramp at the moment, could almost be an excuse to get one.

I realise I’ve done damage driving it for too long after the code first came up. There was once my wife was driving it and it wouldn’t engage at all then after a few attempts it lunged into 3rd. (This is also attribute that makes us think pressure plate as there’s other owners had this precise issue) Also, in frustration I was quick swapping from drive to reverse in the rather silly hope it would clear the issue, so no doubt that’s possibly where the shavings came from.

In regards to the problem arising between 80-90degrees, I’m just assuming that the heat effects the viscosity and therefore the pressure etc, however, for all I know there’s an actual temperature sensor that dictates whether it works or not rather than it being thickness related.
 
First, I would want to be sure that the ECUs are up to date as problems in the code can lead to damage and wear.

Second, I would check the transmission pan, filter(s), and most importantly the magnets. In any gearbox / transmission the magnets are of critical importance to minimizing wear and damage. As the magnets load up on material (they work 24hrs everyday) they loose their effectiveness. If you keep the magnets clean (annually) you can minimize the wear & damage.

Regardless of what's happened, a heavier (higher) viscosity fluid might help if there's been excessive wear. My first thought is to check out Valvoline Maxlife ATF or a similar 6cSt Multi-ATF but I'm not sure about the specifics of a c220d.
 
martinq said:
First, I would want to be sure that the ECUs are up to date as problems in the code can lead to damage and wear.

Second, I would check the transmission pan, filter(s), and most importantly the magnets. In any gearbox / transmission the magnets are of critical importance to minimizing wear and damage. As the magnets load up on material (they work 24hrs everyday) they loose their effectiveness. If you keep the magnets clean (annually) you can minimize the wear & damage.

Regardless of what's happened, a heavier (higher) viscosity fluid might help if there's been excessive wear. My first thought is to check out Valvoline Maxlife ATF or a similar 6cSt Multi-ATF but I'm not sure about the specifics of a c220d.
Click to expand...

IMG_1124.webp
 
Thanks again for the reply. Can I ask, Do you think the oil you mentioned will have more viscosity once the gearbox gets to temperature compared to mercedes own brand?
 
Astro14 said:
With any gearbox, make certain that the fluid is fresh, and the level correct, before diagnosing it.

So, I wouldn’t change to thicker fluid, it’s not going to make much difference, but I would change the fluid to a Mercedes approved fluid, and ensure the proper level as a next step.

I believe your transmission uses a 236.17 - if that’s not right, then please adjust where you search for fluid - but start your fluid search with approved fluids, here:

https://operatingfluids.mercedes-benz.com/sheet/236.17
...
Start with the fluid change and level check.
Click to expand...
The link provided by Astro14 (thanks Astro!) lists several compatible fluids from many MFGs. Which of these are available to you? Also, I'm not sure where you are (UK?) but I'm most familiar with products from NA / Canada.

You also mentioned a Mercedes specialist and a software update. Can you verify with them the status of the engine / transmission updates?
 
There is some discussion of this fluid here:
D

Thread 'Who currently makes the OEM Mercedes transmission fluids?'

I've been looking at the bottles for the OEM Mercedes transmission fluids but don't recognize them. The gear oils are Castrol (they don't even relabel or rebrand them).

Here is an example of the bottle, the OEM 236.17 ultra-low viscosity ATF "FE" for the Jatco 9-speeds. Given that the list of approved oils for this spec is so small, I'm thinking it's made by Fuchs, Shell, Ravenol, or Sinopec....but it doesn't look like any of their bottles. The datasheet says it's made in Germany.

Oddly enough, that bottle design seems to be used by Vaico who I've never even heard of.
  • Like

Looks like MB 236.17 is an ULV (ultra low viscosity) ATF and there's mention of Nissan using the same Jatco 9-speed transmission.

There is a link to the Valvoline Maxlife ATF data sheet on this page:
https://www.valvolineglobal.com/en/maxlife-multi-vehicle-atf/

... on that PDF you will find the fluid specs and a long list of MB 236 fluids that it is compatible / compatible with. Maxlife is listed as a 5.9 cSt fluid at 100C which is what we generally consider a standard 6cSt ATF that is good for the vast majority of ATs in the world in most climates. So yes, this is likely a thicker viscosity ATF than the MB 236.17 if it is indeed a ULV in the 4cSt range.
 
martinq said:
There is some discussion of this fluid here:
D

Thread 'Who currently makes the OEM Mercedes transmission fluids?'

I've been looking at the bottles for the OEM Mercedes transmission fluids but don't recognize them. The gear oils are Castrol (they don't even relabel or rebrand them).

Here is an example of the bottle, the OEM 236.17 ultra-low viscosity ATF "FE" for the Jatco 9-speeds. Given that the list of approved oils for this spec is so small, I'm thinking it's made by Fuchs, Shell, Ravenol, or Sinopec....but it doesn't look like any of their bottles. The datasheet says it's made in Germany.

Oddly enough, that bottle design seems to be used by Vaico who I've never even heard of.
  • Like

Looks like MB 236.17 is an ULV (ultra low viscosity) ATF and there's mention of Nissan using the same Jatco 9-speed transmission.

There is a link to the Valvoline Maxlife ATF data sheet on this page:
https://www.valvolineglobal.com/en/maxlife-multi-vehicle-atf/

... on that PDF you will find the fluid specs and a long list of MB 236 fluids that it is compatible / compatible with. Maxlife is listed as a 5.9 cSt fluid at 100C which is what we generally consider a standard 6cSt ATF that is good for the vast majority of ATs in the world in most climates. So yes, this is likely a thicker viscosity ATF than the MB 236.17 if it is indeed a ULV in the 4cSt range.
Click to expand...
Can you spare a moment to tell me your thoughts on this oil. Seems to have a 7.3 cst.
Millers is very well sought after in uk.
 
Post a link to the product info or spec sheet / PDF.

I didn't see anything about "Millers" on that thread and I haven't heard of them before.
 
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