Power transmitting system for a four-wheel drive vehicle

A power transmitting system for a four-wheel drive vehicle driven by an engine controlled by a throttle and having an automatic transmission, comprising:

• a central differential operatively connected to an output member of the automatic transmission, the central differential having a first side gear and a second side gear;
• a first drive train for transmitting rotation of the first side gear of the central differential to a front drive shaft, the latter being operatively connected to front driving wheels of the vehicle;
• a second drive train for transmitting rotation of the second side gear to a rear drive shaft, the latter being operatively connected to rear driving wheels of the vehicle;
• a fluid operated friction clutch provided between the first and second side gears so as to operatively connect both the side gears for locking the central differential;
• and
• a hydraulic control circuit for applying line pressure of oil in the automatic transmission to the friction clutch so a to engage the clutch at clutch capacity varying according with said line pressure, said line pressure increasing with increase of throttle opening degree, so that distribution of power of the engine to the driving wheels of the vehicle varies with driving conditions of the vehicle.