I don't think you should cut the gear down to 1/4.  I think you can have a coarse mesh on 3/4 of the gear to save computational cost and fit it in the student limit of 128k since you are only up to 50k, but have a fine mesh on 1/4 to have accuracy. You can still limit the simulation to 1/4 turn. The reason for modeling the full gear is you are studying the vibration of the gear, so the mass and stiffness and mass balance are important. You can't get that correct with only 1/4 of the gear.