This gearbox is needed in the mission "No Vacancy" to restore power to the Happy Pig Motel. Not to be confused with "Gearbox Software", the developer of Borderlands 2
The gearbox is a mission item in Borderlands 2
You need to kill a Badass Bullymong in order to get it
It is used in the mission No Vacancy to restore power to the hotel.
Near the Happy Pig Motel