"At full drive" is a phrase that typically refers to something that is operating at maximum capacity or speed. There are a number of synonyms that can be used to convey a similar meaning, such as "at top performance," "at full throttle," "at maximum output," or "at full speed." Other possible options might include "at peak efficiency," "at top gear," or simply "going all out." Ultimately, the choice of synonym will depend on the specific context and the tone or nuance that the speaker or writer wishes to convey. Whatever term is used, however, the implication is that something is performing at its absolute best.