A method for operating a transmission device and a transmission with at least one oil chamber, in which is arranged a wheelset of the transmission device. At the same time, in order to determine the temperature in the oil chamber, an overall level is determined for the oil chamber, wherein an initial value is determined from the overall energy level at the start of the operation of the transmission device with the following steps: determination of a standardized shutdown time as a function of an external temperature and of the overall energy level that is present with the shutdown of the transmission device, determination of a corrected shutdown time as a function of the standardized shutdown time and a measured shutdown time, and determination of the initial value as a function of the corrected shutdown time and of the momentary external temperature.