This paper introduces an analysis of the impact of gear ratio changes on helical gears' shifting dynamics, reaction moment, and contact force. Helical gears are widely used in mechanical systems due to their improved load -bearing capacities and gear properties. The objective of the current study is to investigate the effect of gear contact force on the reaction forces, moments and stresses at different gear ratios is crucial for optimising design and operational efficiency. The study uses a multipronged approach, including dynamic simulations, FEA, and mathematical modelling, to describe helical gears' geometry, tooth profiles, and material characteristics. Dynamic analysis is used to observe how gear ratio changes affect the system's dynamic response. The study systematically modifies these parameters to examine their impact. The first gear moved with 100 rad/s, while the second gear had 10 N.m torque and changed the number of gear teeth to 20, 30, and 40, varying the gear ratio value to observe changes in the simulation process. The distortion value increases with gear ratio, with the highest value observed at 1. The force reaction on the z-axis at 15 and 32 degrees is highest at 350 N, increasing to 540 N at 15 with a gear ratio of 1.5. The largest reaction force is due to gear ratio 2.0. The contact force of a gear pair stiffness is affected by the gear ratio, with constant stiffness quality reaching 670 N at a gear ratio of 2.0 but with greater degree intervals.