How are multiple-disc clutch packs in automatic transmissions generally applied?

Multiple-disc clutch packs in automatic transmissions are primarily applied using hydraulic pressure on a piston. This system utilizes fluid dynamics to engage and disengage the clutch packs, allowing for smooth transitions between gears. When hydraulic pressure is applied to a piston, it moves and pushes against the clutch plates, compressing the clutch pack.

The reason this method is effective is that it allows for precise control over the engagement of the clutch, which is essential for ensuring optimal performance and shifting comfort in an automatic transmission. This hydraulic system can quickly respond to changes in driving conditions, providing the necessary force to engage the clutch without the harshness that might come from mechanical engagement methods.

Other methods, like spring pressure, might be used for different parts or applications within the transmission, but for engaging the clutch packs specifically, hydraulic pressure is the most reliable and efficient method, ensuring the discs are applied evenly and securely for the power transfer from the engine to the transmission.