Overdrive Switch: Testing and Inspection

The electrical controls governing the shift into fourth gear consist of the control switch on the instrument panel and the overdrive solenoid on the valve body. The control switch is in circuit with the solenoid and must be in the ON position to energize the solenoid. The transmission must also have reached third gear range before the shift to fourth gear will occur.

The control switch, valve body solenoid, case connectors and related wiring can all be tested with a 12 volt test lamp or a volt/ohmmeter. Check continuity of each component when diagnosis indicates this is necessary.

Switch and solenoid continuity should be checked whenever the transmission fails to shift into fourth gear range.