When overdrive is engaged, a shaft that is attached to the housing of the torque converter (which is bolted to the flywheel of the engine) is connected by clutch to the planet carrier. as per the problem which you mentioned its indicating the problem is with the shaft that is attached to the housing of the torque converter.
now how exactly the automatic transmission works to get the exact procedure please click on the link directly
http://www.howstuffworks.com/automatic-transmission.htm/printable
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