Abstract: A locking mechanism for demountably securing a solenoid valve assembly within a receptacle in the wall of a transmission housing. A retention means is presented from the frame of the solenoid valve assembly cooperatively to interact with various blocking faces on a pillar means presented from the transmission housing and located adjacent to the receptacle. A stop lug, an engaging surface and a latching dog are each presented from the retention means. First, second and third blocking faces are presented from the pillar means. Engagement of the stop lug with the first blocking face limits the angular range through which the solenoid valve assembly may be rotated within the receptacle. When the stop lug engages the first blocking face, the engaging surface is disposed in opposition to the second blocking face to preclude withdrawal of the solenoid valve assembly from the receptacle.