Based on the search results, there is no widely recognized technical term, software acronym, or established automotive component known as a "tranny pim."

: Because these modules handle high levels of current, they often share a cooling loop with the transmission fluid or a dedicated liquid coolant to prevent overheating.

: The PIM converts DC electricity from the battery into AC electricity to power the electric motors located inside or attached to the transmission.

In hybrid and electric vehicles, the is a critical feature that manages the flow of electricity between the high-voltage battery and the electric motors. If you are referring to the interaction between a transmission and a control module, Feature: Transmission Control & Power Integration