Hello fellow Abaqus users,

I am performing a frequency analysis of a gearbox housing in order to extract natural frequencies. The internal components (shafts, gears, and bearings) are located at different positions inside the housing, but I want to avoid meshing them to reduce complexity.

I know that I can use Mass and Rotary Inertia instead of explicitly modeling these parts, but I am unsure where exactly to apply them and how to properly account for their effects. Specifically:

1. Where should I apply the mass and rotary inertia? (e.g., bearing seats, gear centers, shaft locations)

2. How should I connect these mass elements to the housing? (Rigid Coupling, Distributed Coupling, or another method?)

I've attached the housing image where each gearbox case (highlighted with red) contains shaft, gear, and bearings. 

Any advice or examples from similar projects would be greatly appreciated!