Question Details

I parked my car at he grocery store and when I came out, the car started with no problem. It went into gear with out an issue by sound and visually via the dash. I hit the gas and the car made a mechanical scraping sort of sound and was barely moving, and it felt like I have half in neutral. Reverse was the same thing. I did not make it out of the parking lot. Now it really wont move at all when its in drive or reverse and revving the engine feels like its in neutral but with something winding up and down. If I put the car in neutral, it feels and sounds perfectly normal. No engine lights or warning indicators. I have not been able to hook up to star since its still in the parking lot. I have a feeling its something mechanical but who knows. I transmissions go on these cars but I am hoping for something easier, cheaper to fix. Could this be anything else? I dont recall seeing any fluid or smells coming from the car either.

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MBFanatic  5 months 2 weeks ago

You most likely have lost most of the transmission fluid. These cars are known to leak by the o ring on the transmission lines.

Check out this guide: https://www.youcanic.com/solution/mercedes-7229-transmission-seal-o-ring-leak

Do you notice any leaks?

 

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ChannelZer0  5 months 2 weeks ago

no leaks i can see.  it was parked overnight and no fluid under it. 

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MercedesMedic  5 months 2 weeks ago

Sorry to hear about your troubles. You will have to get the fault codes.

Let us know what you find out. 

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MercedesMedic  5 months 2 weeks ago

Did you read the trouble codes from the TCU?? 

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ChannelZer0  5 months 2 weeks ago

I had a chance to hook up STAR and the fault code was "0720, Mechanical Failure of component Drive Train" The supplementary info said possible causes of fault could be Transmission output speed. I was able to shift into D, R, N and P without and issue. I could hear it shift and see it on the dashboard and in STAR. While in D, I was able to manually paddle shift through the gears and hear them shift in 1st and 2nd but not 3-7. I think that is by default so you dont start in 3rd gear or higher. Is there any chance this is something other than the tranny itself? something connecting the engine to the tranny? I dont think this is a sensor as I could hear something mechanically wrong when it first happened.
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MBFanatic  5 months 1 week ago

The issue here seems to be the transmission. Most likly the valve body but it may also be internal damage as well but that is less common / less likley. How many mile son the S550? Also can you do a full system scan and let us know what other codes come up?

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ChannelZer0  5 months 1 week ago

88k for miles.  

Could a front passenger broken axle cause this?  i took a look and its broke.

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ChannelZer0  5 months 1 week ago

88k for miles.  

Could a front passenger broken axle cause this?  i took a look and its broke.

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MBFanatic  5 months 1 week ago

Yes of course. Just the broken shaft will take all the revolutions and the car won't go anywhere.

That's crazy though. Can you post a picture?

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ChannelZer0  5 months ago

Turned out the front passenger axle broke and was taking all the revolutions.  I didnt grab a picture before I sent the core back out but the spline was beat up and ran out.  Bought a rebuilt one for $1000 and its running like a dream again.

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MercedesMedic  5 months ago

Glad it wasn't the transmission. Did it give you any other symptoms before hand or it just failed with no warning. 

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BMWadict  5 months ago

Thanks for posting the fix. Never axle breaking like this on a Mercedes.