Transmission Control Systems: Description and Operation

When the overdrive off switch is in ON, all four speeds of the automatic transmission will operate. When the overdrive off switch is in OFF, overdrive will not operate.

With the ignition switch in ON or START, fuse 7 applies battery voltage to the overdrive cancel relay and the "O/D OFF" indicator light. When the overdrive off switch is in the OFF position, the overdrive cancel relay will energize and remove battery voltage from the overdrive off solenoid and the overdrive will not operate.

When cruise control is on and accelerating, the cruise control unit will energize the overdrive cancel relay and remove battery voltage from the overdrive off solenoid and the overdrive will not operate. When the set speed is reached, the cruise control unit will deenergize the overdrive cancel relay and allow overdrive to operate.

The "O/D OFF" indicator will only come on with the overdrive off switch in the OFF position.