Grand Caravan V6-3.8L VIN L (2007)
Figure 2 Stator Operation
Torque multiplication is achieved by locking the stator's over-running clutch to its shaft. Under stall conditions (the turbine is stationary), the oil leaving
the turbine blades strikes the face of the stator blades and tries to rotate them in a counterclockwise direction. When this happens the over-running clutch
of the stator locks and holds the stator from rotating. With the stator locked, the oil strikes the stator blades and is redirected into a "helping" direction
before it enters the impeller. This circulation of oil from impeller to turbine, turbine to stator, and stator to impeller, can produce a maximum torque
multiplication of about 2.4:1. As the turbine begins to match the speed of the impeller, the fluid that was hitting the stator in such as way as to cause it to
lock-up is no longer doing so. In this condition of operation, the stator begins to free wheel and the converter acts as a fluid coupling(Figure 2).
TORQUE CONVERTER CLUTCH (TCC)
In a standard torque converter, the impeller and turbine are rotating at about the same speed and the stator is freewheeling, providing no torque
multiplication. By applying the turbine's piston to the front cover's friction material, a total converter engagement can be obtained. The result of this
engagement is a direct 1:1 mechanical link between the engine and the transmission.
The engagement and disengagement of the TCC are automatic and controlled by the Powertrain Control Module (PCM). The engagement cannot be
activated in the lower gears because it eliminates the torque multiplication effect of the torque converter necessary for acceleration. Inputs that determine
clutch engagement are: coolant temperature, vehicle speed and throttle position. The torque converter clutch is engaged by the clutch solenoid on the
valve body. The clutch will engage at approximately 56 km/h (35 mph) with light throttle, after the shift to third gear.
