POST /services/oauth2/token HTTP/1.1
Host: login.salesforce.com/
grant_type=refresh_token&
client_id=3MVG9lKcPoNINVBIPJjdw1J9LLM82HnFVVX19KY1uA5mu0QqEWhqKpoW3svG3XHrXDiCQjK1mdgAvhCscA9GE&client_secret=1955279925675241571&
refresh_token=your token here