Four-wheel drive vehicle

In a vehicle steered by a steering wheel and equipped with four-wheel drive having a transfer case including a center-differential which delivers driving power to both front and rear axle assemblies when needed, and is shiftable between a two-wheel and a four-wheel drive mode of operation and, in said four-wheel drive mode of operation, between a differential-locked and a differential-unlocked drive mode of operation, an axle differential disposed between left and right axles of at least one of said front and rear axle assemblies in association with wheels on said axles which are non-driven when said center-differential is in said two-wheel drive mode of operation, said one axle assembly being divided and delivering driving power differentially to said left and right axles thereof, and free-wheeling drive means with clutch means incorporated in said one axle assembly, said clutch means being disposed between said axle differential and one of said axles to operationally couple and uncouple said one axle from said axle differential, said free-wheeling drive means being actuated to force said clutch means to operationally disconnect said one axle from said axle differential so as to interrupt the transmission of driving power between said axle differential and said wheel secured to said one axle when said center-differential is in said two-wheel drive mode of operation, or to operationally connect said axle differential and said one axle so as to provide said transmission of driving power between said axle differential and said wheel on said one axle when said center-differential is in said four-wheel drive mode of operation, the improvement comprising:

• detecting means for detecting whether said free-wheeling drive means is actuated to interrupt or provide said transmission of driving power;
• and
• control means coupled to said detecting means for forcing said center-differential to shift from said four-wheel differential-unlocked drive mode of operation to said two-wheel drive mode or said four-wheel differential-locked mode when said detecting means detects that said free-wheeling drive means is actuated to interrupt said transmission of driving power while said center-differential is in said four-wheel differential-unlocked drive mode of operation.