What part of a vehicle changes the engine speed related to all wheels in an all-wheel-drive setup?

In an all-wheel-drive setup, the transmission plays a crucial role in altering the engine speed and subsequently distributing that power to all four wheels. The transmission system facilitates this by adjusting the ratio of engine speed to wheel speed, allowing for efficient power management under various driving conditions.

The transmission is responsible for changing gears which can either increase torque to the wheels at lower speeds or enhance fuel efficiency at higher speeds. It engages different gear ratios to optimize the vehicle's performance, whether accelerating from a stop or traveling at high speed on the highway.

This function is vital for maintaining traction and stability across all four wheels, especially in varying conditions like wet or slippery roads. The drive shaft, while also important, primarily transmits the power from the transmission to the wheels but does not have the capability to change speed by itself. Gearbox usually refers to a component of the transmission responsible for managing gear ratios, and the brake system, while crucial for stopping and control, does not influence the engine speed or power distribution.