I need help figuring out why the engine is shaking so badly?

I need help figuring out why this is shaking so badly. It only occurs when it's in drive mode and at the stop lights. Now I replaced the tensioner and it's still shaking. help me please. Another question I have is that when I put the car in reverse, I hear a lot thump from the transmission. I recently replaced both axles and some transmission fluid did leak out, but this been happening before I replaced them so will I need a transmission fluid and filter change to see if that helps or.