Technician A is correct. In a final drive unit, the pinion gear does drive the ring gear. This is a common setup in rear-wheel-drive vehicles where the pinion gear is connected to the drive shaft and transfers power to the ring gear which is attached to the differential. This mechanism allows the wheels to turn at different speeds while receiving power from the engine.
Technician B is incorrect. Most final drive units on rear-wheel-drive vehicles are not lubricated with automatic transmission fluid. Instead, they are typically lubricated with gear oil or differential fluid. These fluids are specifically designed to provide lubrication and cooling properties suitable for the high pressures and loads experienced in the final drive unit.
Therefore, the correct answer is:
a) Technician A only
