Chrysler Full-Size Trucks 1967-1988 Repair Guide

Neutral Safety Switch



See Figures 1 and 2

The neutral safety switch is thread mounted into the transmission case. When the gearshift lever is placed in either the Park or Neutral position, a cam, which is attached to the transmission throttle lever inside the transmission, contacts the neutral safety switch and provides a ground to complete the starter solenoid circuit.

The back-up light switch is incorporated into the neutral safety switch. The center terminal is for the neutral safety switch and the two outer terminals are for the back-up lamps.

Click image to see an enlarged view

Fig. Fig. 1: Looking up at the neutral safety/backup light switch with the pan removed

There is no adjustment for the switch. If a malfunction occurs, the switch must be removed and replaced. To remove the switch:

  1. Disconnect the negative battery cable.
  3. Raise and support the vehicle on jackstands.
  5. Disconnect the electrical leads and unscrew the switch. Use a drain pan to catch the transmission fluid.

Click image to see an enlarged view

Fig. Fig. 2: External control on 727, 904 and 999 transmissions

To install:
  1. Using a new seal, install the new switch and torque it to 24 ft. lbs. (32 Nm).
  3. Remove the jackstands and lower the vehicle.
  5. Connect the negative battery cable.
  7. Pour approximately four quarts of ATF+3 fluid through the filler tube.
  9. Start the engine and idle it for at least 2 minutes.
  11. Set the parking brake and move the selector through each position, ending in Park.
  13. Add sufficient fluid to bring the level to the FULL mark on the dipstick. The level should be checked in Park, with the engine idling at normal operating temperature.