Abstract: An internally toothed member is shown suitable for use as a clutch drum in an automatic transmission. The internally toothed member has the shape of a cup with an open end and a central axis. The cup-shaped member has first internal teeth extending in the axial direction and second internal teeth extending further toward the open end of the member than the first internal teeth. The internal teeth are each formed on an inner circumferential surface of the cup-shaped member in each of a plurality of locations spaced in the circumferential direction. Also, a groove for receiving a snap ring is formed in the second internal teeth closer to the open end than end faces of the first internal teeth facing the open end. Because the first and second internal teeth are formed projecting radially inward, they do not lower the rigidity of the internally toothed member.

Abstract: A control system for an automatic transmission includes a clutch for transmitting the rotation of a fluid transmission unit to a speed change mechanism of a transmission and a hydraulic servo for applying/releasing the clutch. A stop state detector is provided for detecting the stop state of the vehicle. A release control oil pressure changer lowers the oil pressure of the hydraulic servo by a first set pressure when the vehicle stop state is detected. An in-neutral control oil pressure changer raises the oil pressure of the hydraulic servo by a second set pressure, when the difference between the input side RPM and the output side RPM of the fluid transmission unit has not changed, and lowers the same by a third set pressure when the rotational speed difference has changed. The first set pressure is different from the second and third set pressures.