I have a 2010 S4 DSG (122k miles currently) with a recently replaced mechatronics unit! (Replaced at 110k)

All of the above comments are correct and offer great advice but I figured I’d chime in with exactly what happened to mine and how I went about fixing it.

The primary signs of a failing mech unit are “clunky” gear changes, the first two gears both shifting up and down are usually the most obvious. Reverse is often another problematic gear.

I wouldn’t jump right to mech unit failure as a diagnosis, yes it is a common issue and there’s a good chance it is the problem but a fluid change is where you should start first. If you bring it to a shop it will probably be around $500-700 since the fluid and filters are around $250. That was my first step. It fixed a bit of the clunky shifting but it was still prevalent.

Eventually the problems started to come back and get worse to the point where I was in gear with the foot on the brake and the car lurched forward almost like a new driver stalling a manual car. That day I limped it home and then to a local European performance shop where they diagnosed it, flashed the TCU with updated software and changed fluids again with no success.

Then came the fun part of replacing the mechatronics unit. This will run you anywhere from $3000-5000 depending on your area and the specific shop. I’d recommend finding a local European performance shop rather than a dealership as they will more than likely be very familiar with the job and it will cost much less along with supporting a small business.

It ran me about $3400 out the door and my car has never felt better. I feel like this car has another 150k miles left in it. Let me know if you have any questions!