2006 Nissan Maxima Question: Could the transmission mount be causing a problem?

I took my 2006 Nissian Maxima to a Nissian dealer to have it checked out for transmission issues; because I am experiencing some jerking when I accelarate, I was told that the front motor mount and the trans mount were broken, what I what to know now is that what could be causing my car to shift hard when changing gears.