I can see that to be true on the cruise control circuit, but then again, there's more to the cruise control than just the brake switch to cause it to fail. Check the vac. line on the actuator and the electrical connector for the solenoid. As for the overdrive, IF you have a Throttle valve cable on the throttle body , you can adjust that to fine tune the shift points.
The only time a Transmission is affected by a brake switch is if it has an electronic lock up torque converter.