Everytime i accelerate car shifts hard and it seems to make like a knock sound under the hood. i had i check says its the motor mount but i already replace it. i had the transmission check mechanics saids it ok. any idea what it is? thanks!

 

There are several mounts, be sure all of them are good. Then check for proper adjustment of the throttle control cable....last, is the trans fluid full and "clean"-when was it last changed.