I get a very hard and loud jerk when I shift from drive to first. on 1999 Mercury Sable

every time I shift from park to first,it jerks hard.when I shift from park to reverse,or from drive to reverse or from drive to first or second, I don't feel it. I was told I have to rebuild the trans, then I was told it wasn't the trans. Please help.

Asked by for the 1999 Mercury Sable
The things that could cause this is the an internal transmission problem, badly worn drive shaft joints or badly worn engine mounts, get someone to properly check the car prior to them jumping to conclusions as to what is wrong.