Automatic transmission and warming-up method for automatic transmission

An automatic transmission, comprising:

• a plurality of rotary shafts that includes an input shaft including a clutch and an output shaft for outputting a drive force;
• a plurality of gears including an output-side gear provided on the output shaft;
• a plurality of synchromesh mechanisms that includes an output-side synchromesh mechanism capable of coupling between the output shaft and the output-side gear;
• a lubricant oil reservoir that reserves lubricant oil stirred up by rotation of at least one of the plurality of gears;
• a shift position detection section that detects which of a plurality of shift positions including a neutral position is selected;
• and
• a control section that actuates at least one of the plurality of synchromesh mechanisms other than the output-side synchromesh mechanism for causing the at least one of the plurality of synchromesh mechanisms to couple between at least one of the plurality of rotary shafts other than the output shaft and at least one of the plurality of gears other than the output-side gear, and then puts the clutch into a connected state, when the neutral position is detected by the shift position detection section.