AUTOMATIC TRANSMISSION – GM 5L40-E DESCRIPTION AND OPERATION Nine clutch mechanisms are used in the LE transmission unit. There are six drive clutches and three brake clutches which comprise of one or more friction plates depending on the output they control. Atypical clutch will consist of a number of steel outer plates and inner plates with friction material bonded to each face. When the clutch is operated, the torque transmitted through the plates is dependant on the friction of the plates and the pressure applied to them. If one of these two factors is inadequate then clutch slippage will occur. Depending on the application, the outer and inner plates will be splined to the hub or housing. This allows the drive from the hub for instance to be connected or braked by the housing when the clutch is applied. The clutch is actuated hydraulically by a piston arrangement which applies pressure to drive the outer and inner plates together. The hydraulic pressure is received from the applicable shift valve and damped by the relevant accumulator to provide a smooth clutch take-up. Springs are fitted to oppose the piston movement. When the apply pressure is decayed, the springs move the piston away from the plates and ensure that they are fully disengaged. If the plates are allowed to 'drag, the friction decreases the efficiency of the transmission and causes premature wear of the friction plates.