transimission on 2005 Nissan Altima

when the trans shifts from 1st to 2nd it shifts real hard sometime but not all the time. It has 77,000 miles and the fluid has never been changed. Any ideas

Asked by for the 2005 Nissan Altima
I would start by doing a service, a flush is the preferred way, on the fluid and a replacement of the filter ( if equipped ). I would also check for codes to see if there is a sensor or solenoid acting up. Is there a Check Engine or Service Engine Soon Light On?