We were 4 students in final year mechanical engineering. For our CAD/CAM/CAE project in 4th year, we decided to work on a rear differential gearbox. A marvelous work of engineering that allows power to be distributed to the rear wheels without creating wheel slippage. Not our idea of course, it was invented more than a century ago. We simply took a car (INFINITI G35), and reverse engineered a rear differential that would be optimal for the engine specs, wheel specs and space constraints. Calculations were done on paper, and consequently this design went to CAE simulation for verification.
It was also machined in NX Computer-Aided- Manufacturing.