Shift Valve Operation

The shift valves are moved by a combination of throttle and governor pressure. The governor pressure is generated by electrical components.

The conditions under which a shift to fourth will not occur are:
- Overdrive switch is Off
- Transmission fluid temperature is below 10 °C (50 °F) or above 121 °C (250 °F)
- Shift to third not yet completed
- Vehicle speed too low for 3-4 shift to occur
- Battery temperature below -5 °F.