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Transmission problem auto

Hi guys
Please bear with me. Lady here

I have a 1999 Mercedes-Benz C240 (w202)
It leaks oil. My mechanic said it is transmission fluid and not engine oil. He can’t work on auto gearboxes. He says there is a switch that needs replacing on the gearbox.
Now he also told me I can drive it as it is and just keep the fluid full till I can afford to repair.
I have been doing this. In the last 2 weeks I have driven approximately 700km. I have been topping up a little at a time when it feels dry on gear change. I have put in approximately a bottle now. I do not have a dips tick to test the level and neither does he. Today my car felt as though it was laboring and revving high. It also felt as though it was missing 5th gear. At one stage I couldn’t travel over 90km/h.
Any advise would be appreciated as I am financially strained at the moment. Am wondering if I put too much or too little? Am I damaging the vehicle?
Please and thanks

You can get a dip stick from RockAuto to check the transmission fluid level.

When an automatic transmission doesn’t shift and the engine revs, this is called slipping.

Slipping means the clutches aren’t engaging properly. When this happens it creates heat which breaks down the transmission fluid which then damages the transmission.

It’s better to slightly overfill the transmission with transmission fluid than to under fill it as this will prevent slipping.

So to prevent further damage to the transmission, have the leaking switch replaced.


Considering I barely know how to change a tyre I feel I am going to have to take it in

The short answer is you are either damaging your car now, or you will be shortly. Without an accurate way to measure how much fluid you are losing, you have no way to know how much to add. There is no way to estimate this. If you drive while you are waiting for a dipstick to come in the mail, you could easily destroy the transmission.

The sad truth is that you have to get this fixed, and every mile you drive under these circumstances puts a very expensive transmission at risk.

If you’re not keeping the fluid at the correct level, you can kill your transmission quickly. If you can’t afford to fix a leak, you certainly won’t be able to afford replacing the transmission if it comes to that.

Yep, slipping on an automatic transmission (gear box) will kill it in a hurry because there are clutches in it that it needs the proper fluid level to keep the clutches engaged. Do not allow it to slip or you will be putting in a new transmission instead of fixing the leak.

Hope you’re using the correct fluid

How many miles on this transmission

Has the fluid and filter EVER been serviced

Are you in the UK . . . ?

There was no 1999 C240 sold in the US . . . and you did use the term “tyres” :wink:

BTW . . . you said a switch needs replacing on the gearbox

Do you mean the shifter, or the actual transmission itself?

I have a nagging suspicion THIS is perhaps what is leaking . . . this is the most common leak on your transmission

This part also sometimes fails. The various solenoids attach to it, and it contains the temperature sensor.

I am going to offer two pieces of unrequested advice .

  1. I don’t believe in credit card usage but in this case having a real transmission person look at this could be cheaper than having to replace a complete transmission because at this rate that is what is going to happen.

  2. After solving this problem I would replace that old C240 with a more main stream vehicle . Old luxury vehicles are not for people with limited funds.

I have an automatic in my truck. It’s been under-filled and over-filled at times, and there’s symptoms either way. But I think it might be very difficult for the driver to tell if an automatic transmission is over-filled or just by the way it is behaving. There’s no problem with your mechanic’s suggestion to top it off occasionally if you can’t afford to fix what’s leaking; but until you have a method to measure the fluid level accurately, suggest to stop driving. Public transport or rent a car in the meantime. You’ll be money ahead.

Thank you all for your input negative and positive haha.
I am merely financially strained right now. Not normally.
But I think what I am reading here makes sense. I have overfilled.
Now it’s slipping. Sadly I am in South Africa.
I will get it off to someone asap

The wiring connector housing shown in DB4960’s link is a common and inexpensive leak repair. You should have someone inspect the transmission for leaks.

Hi guys
Thanks for all the comments.
After diagnostics…
It is not overfilled as it has an overflow
It is the Electro plate on the transmission.
Transmission is heating and switching to lymph mode

If you are absolutely sure it’s JUST the conductor plate and nothing else . . .

I would replace that conductor plate, the electrical adapter, fluid, filter and gasket

The conductor plate is very easy to replace. You just have to remove the valve body first. The conductor plate sits on top of it, and the solenoids plug into the conductor plate. But you have to torque the valve body bolts. If you’re not careful, you’ll strip the threads out.

Make sure to also drain the torque converter . . . it has a drain plug

Should be right around 8 quarts total . . . fluid needs to be 722.6 compatible, or NAG1 compatible. Same thing

I hope whoever did the diagnostics was correct . . . the fact that it’s “heating” makes me wonder if there’s something more serious going on

How many miles on the car?

Has the fluid and filter ever been serviced?

Some further words to the wise . . . drain the fluid into a clean tub or pan. Do NOT discard it just yet. Then drop the pan, and inspect it, as well as that fluid. If it’s full of metal shavings or clutch material, that transmission is done for. And if that is the case, then you can forget all about replacing the conductor plate, electrical plug, etc., because then you need to get your transmission overhauled

He is also going to service the transmission and change the fluid. Also fix a small leak on it. He said there might be something else wrong too. He will only know once it’s stripped