Stator One-way Clutch Function


The direction of the fluid entering the stator from the turbine runner depends on the difference in the rotational speeds between the pump impeller and turbine runner.

1. When the rotation speed difference is large

The fluid strikes the front surfaces of the stator vanes, causing the stator to rotate in the direction opposite that of the direction in which the pump impeller rotates. However, the pump impeller cannot rotate in the opposite direction because the stator is locked by the one-way clutch. Therefore, the direction of the fluid flow is changed.

2. When the rotation speed difference is small

Some of the fluid flowing from the turbine runner flows into the rear surface of the stator vanes. When the speed difference is at minimum, much of the fluid sent from the turbine runner contacts the rear surface of the stator vanes. In such a case, the stator vanes interfere with the fluid flow. The one-way clutch makes the stator idle in the same direction that the pump impeller is rotating and the fluid returns smoothly to the pump impeller.


When the stator cannot be locked, symptoms of acceleration failure occur due to the system being in the coupling range. On the other hand, when the stator cannot rotate freely, the system remains in converter range and the symptom occurs such the speed does not increase above a certain speed. Inspection of One-way Clutch

Inspection of One-way Clutch

One-way clutch inspection method

(1) Insert the SST in the inner race of the one-way clutch.

(2) Install the SST so that it fits in the notch of the converter hub and other race of the one-way clutch. (3) With the torque converter standing on its side, the clutch should lock when turned counterclockwise, and should rotate freely and smoothly when turned clockwise. If necessary, clean the converter and retest the clutch. Replace the converter if the clutch still fails the test.

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