Dynamic all wheel drive

An all wheel drive and control apparatus for a vehicle powertrain having a pair of normally driven wheels and a pair of normally undriven wheels comprising:

• a housing driven in unison with the normally driven wheels;
• a reservoir for storing hydraulic fluid;
• first and second selectively engageable fluid operated clutch means disposed between said housing and the normally undriven wheels each including a pump having a fluid inlet, a fluid outlet, a first portion driven by said housing, and a second portion rotating with said normally undriven wheels, said pumps being effective to supply fluid pressure to engage said clutch means when said pumps are selectively connected with said reservoir;
• and
• a control valve member disposed in fluid flow relation between said reservoir and said inlet of said pumps and being responsive to a loss of traction at said normally driven wheels to connect said reservoir with said pumps only during said loss of traction.

An all wheel drive and control apparatus for a vehicle powertrain having a pair of normally driven wheels and a pair of normally undriven wheels comprising:

• a housing driven in unison with the normally driven wheels;
• first and second selectively engageable fluid operated clutch means disposed between said housing and the normally undriven wheels each including a pump having, an inlet, an outlet, a first portion driven by said housing, and a second portion rotating with said normally undriven wheels, said pumps being effective to selectively supply fluid pressure to engage said clutch means;
• a reservoir for storing hydraulic fluid;
• and
• a control valve mechanism disposed in fluid flow relation between said reservoir and said inlet of said pumps and being responsive to a loss of traction at said normally driven wheels to selectively connect said pumps with said reservoir to deliver pressurized fluid to said clutch means only during said loss of traction.