Abstract: A synchronizing apparatus for a power transmission comprises a shaft for rotation in response to a power source, a clutch hub fixed to the shaft for rotation therewith, the hub including an outer spline thereon; a sleeve including an inner spline for engaging the outer spline of the clutch hub, and having an inner frictional face radially outward from the inner spline; a gear rotatably mounted on the shaft including an outer spline surface having first and second grooves therein, and a circular groove between the first and second grooves; the spline surface also having a pair of adjoining sloped portions thereon, each having a different degree of slope; a synchronizing ring including an outer frictional surface for frictional contact with the inner frictional face, and an inner projection for engaging the outer spline surface of the gear and; a spring mounted in the circular groove for movement along the two sloped portions of the outer spline surface for biasing the ring toward the sleeve.

Abstract: A two-wheel/four-wheel automatic change-over device in an automobile transfer apparatus is disclosed. In the transfer apparatus in which driving forces are transmitted directly from a transmission to front two wheels or rear two wheels and also transmitted through a wet-type multiple disc clutch to the other two wheels, the two-wheel/four-wheel change-over device has a change-over control unit for changing over from two-wheel drive to four-wheel drive. This unit automatically effects an engagement and a release of a wet-type multiple disc clutch in response to a signal of high speed travelling, a signal of slope travelling, a signal of quick acceleration travelling, a slip signal obtained from a relation between a real car speed and rotation of the wheels and a signal of a selector switch. In such a constitution, the wet-type multiple disc clutch is usually hydraulic-controlled so that it is differentiable in time of the four-wheel travelling.

Abstract: A control system for a four wheel drive vehicle is disclosed which either prevents the transmitting of the power of an internal combustion engine incorrectly or gives a warning signal indicative of incorrect operation. The control system includes two sensors for separately detecting the rotational frequency of front and rear propeller shafts, a control circuit for determining the rotational frequency difference between the front and rear propeller shafts and for generating control signals relative to a predetermined set point. A contact or a switch is operated by the control circuit. In one embodiment, an alarm buzzer and an alarm lamp are also provided.