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Q: Transmission leak stuck choppy - 2005 Mercedes Benz C55 AMG

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I have a small transmission leak, and my car has been really choppy shifting the past few weeks. It get’s stuck in gear, and I’m not able to shift through the number or letter modes. This morning was the worst. It was stuck in first gear, and I drove at 20 mph to the dealership to get it fixed. They said I need a new Transmission Control Unit, so I need to do it myself. So I drove back home at 20 mph. Is this really hard to do? Can you give me some step by step directions on how to install it? I would really appreciate it.

Hello. From the symptoms you describe, it would appear that the vehicle is experiencing issues that have put it into limp, power reduction mode. If the TCU requires replacement, it can usually be found in the engine bay on the passenger side. You also mention that the vehicle has a transmission leak. I would first address the leak, as it may very well be possible that a leak caused the TCU to fail.

This is a commonly known issue that can sometimes affect AMG vehicles. Unless you are familiar with automotive repair, I would advise that you do not attempt these repairs on your own, as a luxury vehicle such as this may be difficult to work on. I would recommend having a professional technician first diagnose the vehicle, and then move forward with the appropriate repairs.

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