how do i know if my engine mount needs replacing 2012 mercedes benz s550 4matic

What is your question?

My car vibrates when driving between 45 and 70 mph and then levels out. Sometime you can feel it throu the steering wheel. I just replace the torque converter but before i did that my car was ride very smooth and now it does not. The dealer give me a estimate of 2,000 to replace the motor mounts. I would just like more information on this matter.

What makes this problem better or worse?

driving under 40 and over 70

How long has your 2006 Mercedes-Benz S500 had this problem?

2 weeeks