Chevrolet TrailBlazer, Service Manual

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Torque converter
The torque converter housing is rotated by the engine's crankshaft, and turns the impeller.
The impeller then spins the turbine, which gives motion to the turbine shaft, driving the
gears.
The impeller is turning faster than the turbine. It picks up fluid at the center of the converter
and, through centrifugal force, slings it outward. Since the outer edge of the converter
moves faster than the portions at the center, the fluid picks up speed.
The fluid then enters the outer edge of the turbine blades. It then travels back toward the
center of the converter case along the turbine blades. After making contact with the turbine
blades, the fluid loses the energy picked up in the impeller.
If the fluid was now returned directly into the impeller, both halves of the converter would
have to turn at approximately the same speed at all times, and torque input and output
would both be the same.
In flowing through the impeller and turbine, the fluid picks up two types of flow, or flow in
two separate directions. It flows through the turbine blades, and it spins with the engine.
The stator, whose blades are stationary when the vehicle is being accelerated at low
speeds, converts one type of flow into another. Instead of allowing the fluid to flow straight
back into the impeller, the stator's curved blades turn the fluid almost 90° toward the
direction of rotation of the engine. Thus the fluid does not flow as fast toward the impeller,
but is already spinning when the impeller picks it up. This has the effect of allowing the