My mercedes benz S65AMG jerks and makes a funny noise like a motor cycle.

I hate replacing parts without testing them and proving they have failed. Are there misfire codes set, check engine light on? If so a scan tool will be needed to retrieve codes stored in the computer of your car. The codes stored in the computer would indicate where the problem is or at least give a basic starting point to do tests. It's so difficult to guess without being able to experience the problem first hand and at least do some basic diagnostic test.A professional grade scan tool reads stored trouble codes, pending trouble codes, looks at live sensor data so you can look at a sensors performance and output signals without having to do intensive testing at each sensor, (cheaper scan tools have limited capabilities and may only read the trouble code stored).There is a professional service called Identafix. http://www.identifix.com/info/about_us.htm They only deal with professional repair shops. They are in the Minnesota 651-633-8007 Your auto repair shop do all their diagnosis tests, and discuss your problem with a team of professional technicians great service cheap and very bright people. If the repair shop that are repairing your car are stumped this is a great service. This company only deal with automotive repair shops and don't answer questions for the general public but are an amazing knowledge base.