A special fixture and test procedure is described which measures gear tooth bending stress in high contact ratio truck transmission spur gearing. A mathematical model which includes the effects of involute profile modifications, spacing variations, crown, and lead variations is described and its results are compared to the test measurements. Finite element analysis verification and disadvantages are described. Truck transmission dynamic measurement results of gear bending stress and torque split between the two twin countershafts are reported. Conclusions include that the mathematical model bending stress results compare favorably to test measurements and the twin countershafts have nearly equal torque load and small dynamic load variations with speed.