Pacs - Tranny

: Discs coated with high-grip material that grab onto the steel plates when hydraulic pressure is applied.

: Oil pressure from the transmission's pump is the force that physically "packs" these plates together to transfer power. tranny pacs

In an automotive context, "tranny pacs" (more formally known as ) are the critical internal components of an automatic transmission responsible for shifting gears . These packs consist of a series of alternating friction and steel discs stacked within a drum. When the transmission’s "brain," or valve body, directs hydraulic fluid to a specific drum, a piston squeezes the pack together. This pressure locks the discs, engaging the corresponding planetary gear set to change the vehicle's speed or direction. : Discs coated with high-grip material that grab