When a rear wheel drive car accelerates around a bend at high speeds, the drive shaft is subject to both bending and torsional loads. the accelerating torque is reasonably constant at 400 nm while the bending moment at a critical section varies due to cornering and can be expressed in n-m as m = 250 + 800sinωt. design the shaft for infinite life using de-goodman criterion assuming the shaft is uniform cross-section. the reliability in estimating the endurance limit should be at least 99% and a safety factor of 4.5 should be used in the design. the shaft is forged from 1080 steel of ultimate strength 620 mpa and yield strength 380 mpa.