W221 S550 wont engage tranmission

  mercedes/s-class/2006-2013

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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