When we select D the car really shakes with a loud thud into gear and then works fine. Take it out of drive and put it in again same problem. Any ideas
First check the trans fluid level following the instructions in the handbook and verify the level is correct. Take a clean white rag and dip the trans oil and wipe it on the rag. Does it look brown and smell burnt? If so this is an indication of expensive internal wear. The fluid should look 'clear red'. Sometimes advanced wear in the gearbox is not only seen as a burnt brown fluid but indicated by tiny metallic particles (Look like fine brass filings) suspended in the oil itself. Best advice is look to swap it for another gearbox if it exhibits the latter of these symtoms as auto-box repair is not cheap !
