ClassicCar

So I have replaced the tranni, engine is newly rebuilt, brakes all redone. Problem is that when I start it it has a rough idle, when I shift from Park or Neutral to any other moving gear the entire engine bogs down, the idle drops and the car shakes tremendously. If I accelerate it smooths out. When I engage the brakes the rpms drop and the shaking and dieing come back. My fluid level is good on the tranni anyone have any ideas. Anything at all, I have hit my wits end and just want to enjoy driving this beautiful car. Thanks for your time and information.