Servicing a transmission that has lacked for service for many miles has resulted in immediate problems on several occasions for me. Adding one of several transmission “tune up” products always put the vehicle back in service. In recent years I included adding the “tune up” product as part of the service and eliminated the irate customer calls. Trans_X, Trans-Medic, and Sea-Foam all seem about equal. The heavier additives like Lucas never seemed to improve the situation.