1996 olds aurora possiblt tran

1996 aurora great car with whirring sound. whirring sound comes from the driver side underhood between resevoir and engine space. whirrs in park and neutral. when foot on brake and u put in gear it stops long as foot is on brake. when u start driving u can hear. not as much because car moving and whirring faster so not as loud. i don't know what this. if u can help me tell me. not sure if its trans or something else. please help. fluid was kind of pink like pepto bismo