Input shaft - transfers power from the torque converter to internal drive members and gearsets.

Oil pump - produces pressure to operate hydraulic components in the transmission.

Valve body - operated by shift lever and sensors; controls oil flow to pistons and servos.

Pistons and servos - actuates the bands and clutches.

Bands and clutches - applies clamping or driving pressure on different parts of gearsets to operate them.

Planetary gears - provides different gear ratios and reverse gear.

Output shaft - transfers engine torque from the gearsets to the drive shaft and rear wheels.

TORQUE CONVERTERS

The torque converter is a fluid clutch that performs the same basic function as a manual transmission dry friction clutch (fig. 4-24). It provides a means of uncoupling the engine for stopping the vehicle in gear. It also provides a means of coupling the engine for acceleration.

A torque converter has four basic parts:

1. Outer housing - normally made of two pieces of steel welded together in a doughnut shape, housing the impeller, stator, and turbine. The housing is filled with transmission fluid.

2. Impeller - driving member that produces oil movement inside the converter whenever the engine is running. The impeller is also called the converter pump.

3. Turbine - a driven fan splined to the input shaft of the automatic transmission. Placed in front of

Figure 4-24. - Torque converter, partial cutaway view.