Mercedes-Benz 2003 C320 Transmission - Mercedes-Benz Forum
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post #1 of 5 (permalink) Old 05-30-2019, 07:19 PM Thread Starter
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Mercedes-Benz 2003 C320 Transmission

Hi Everyone,

I recently bought a 2003 MB C320 with 90,000 miles. I had a pre-purchase inspection by a local independent MB Auto place. They told me the transmission was leaking a bit and recommended service.

I have not noticed anything wrong with the transmission, no shifting issues, no lights, etc, just a warning the mechanic gave me. (It's an automatic btw).

At the shop they told me the transmission fluid should be changed every so often and people don't like to do it b/c of the cost, and that's maybe why the fluid is leaking, they recommended service. But then I looked through the owners manual and it said the transmission fluid NEVER needs to be changed, That if you notice leaks take it to an authorized MB dealer, that's it- I've never seen such a short set of instructions for a whole car transmission.

I have not noticed any leaks, but I don't know what to look for and am not particularly savvy with that stuff. I am confused about the owner's manual saying the transmission fluid never needs to be changed and the seemingly conflicting information given to me by the mechanic. I had a friend say some of these cars have sealed transmissions, that don't need fluid changes? But he was just guessing.

What should I do? I just want to make sure I maintain my new car properly.

Thank you for any advice!
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post #2 of 5 (permalink) Old 05-30-2019, 07:48 PM
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The owners manual is wrong, listen to your mechanic. He speaks from experience. Have him fix the leak as well.
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post #3 of 5 (permalink) Old 05-30-2019, 08:11 PM
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The leak is most likely at the electrical connector (pilot bushing) to the transmission. It is usually internal and will not be visible from the outside unless very severe.

If it is not fixed, fluid will wick up into your transmission control module thru the wiring harness and put your transmission into limp mode.

MB now recommends servicing transmission at a regular interval. I do mine every 40K miles.

Last edited by 260e crusier; 05-31-2019 at 08:16 AM.
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post #4 of 5 (permalink) Old 05-30-2019, 10:49 PM
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I was speaking to my local mechanic (an honest one) just yesterday about these "No Service Transmissions" and longer service intervals and they are all about appeasing EU Emissions targets only.

They are not about protecting the Car's engine at all.

Setting longer service intervals theoretically reduces Engine Oil pollution by 50% and where they cannot make their targets fit they do away with any transmission servicing and tell the EU Bureaucrats how good they are doing. They are not at all concerned about the rotting hulk a car becomes when it breaks down and repair jobs runs into the multiple '000's and therefore too expensive to correct.

The fluid is expensive but well worth the cost.

A few recommendations for YouTube channels:

AUTODOC: They have dedicated W203 Repair/Replacement Tutorials on most things that you can do at home. (Excellent viewing)
LEGITSTREETCARS: Alex works on mainly AMG V8's but it is amazing how much you can learn from him regarding Brakes,Suspension, Servicing (inc Tranmissions, though there are complexities to this) He was an MB "Journeyman" Mechanic).
TAVARISH: He is funny, but smart too.

These guys along with this forum, will keep you and your Car happy for along time.
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post #5 of 5 (permalink) Old 05-31-2019, 07:17 PM
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Even though the 722.6 transmission was sold as "sealed for life", there were some unofficial dealer communications suggesting that it would be OK to change the fluid every 70K miles. The 722.9 transmission was also sold as sealed fro life, but after some early problems, MBZ officially called for a one-time fluid and filter change at 40K miles. But later, they changed that to "every" 40K miles. Other than the extra gears, there are no differences in the 722.9 and 722.6, so "what's good for the goose is good for the gander". Have the transmission serviced and get the leak fixed while you're at it.



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