The function of the axle drive shaft is to transfer the engine torque from the gearbox or differential gear to the wheels. It must also endure for all dynamic loads resulted from variations in angle or length during driving from contact the vehicle tire with road. Most problems with the axle drive shaft manifest themselves in the form of knocking noises when driving around tight corners, accelerating, or when the suspension is being compressed and extended where the drive shaft becomes weakened and more subject to stress failure due to dynamic torsion, tensile, shear, and compression. This work consists of effect of heat treatment type applied to the steels CK45 on the resulted behavior of the fatigue and toughness and study of these heat treatments on the microstructure and micro-hardness across the specimens depth. Where this heat treatable alloy usually used in drive-shafts in vehicles which exposed to a dynamic loads and the goal is to investigate the best relation between heat treatment and the service conditions. However, microstructural characterization and microhardness measurements revealed that the shaft belongs to medium carbon steel contains ferrite and pearlite, measuring the toughness for four heat treatments to obtain the best case and measuring the fatigue life of quenching case has better life compared to other cases. The oil quenching gives best toughness value of 30 Kj/m2 and the worst value obtained for as received one giving 7 Kj/m2 and the maximum fatigue life under stress of 375 MPa belonged to oil quenching treatment and it was 75000 cycles to failure while the as-received alloy reported 2000 cycles at failure. The S-N curve of the four cases based on Basquin formula with correlation factor (R2) close to one. And the water quenching steel alloy recorded higher curve component to other cases.