Dynamics of Machines - Question and answers

I'm working on a project for a mechanical design class where I'm simulating a spur gear system using software like Adams or similar tools. The system has two gears with a 2:1 ratio, and I've applied a constant input torque. However, the output torque shows significant fluctuations, even though I've accounted for backlash and friction. I've tried adjusting mesh stiffness and damping parameters, but the issue persists. What specific factors should I check or modify to reduce these fluctuations?