See Figure 1GM Turbo Hydra-Matic
This switch prevents the engine from being started in any position other than Park or Neutral. It also controls the backup lights.
- Set the parking brake.
- Make sure the shift linkage is adjusted correctly.
- Remove the switch from the base of the steering column, inside the vehicle.
- Shift into Park and lock the column by removing the key.
- Move the switch lever until it aligns with the letter P on the back of the switch. Insert a 3 / 32 in. drill bit in the hole below the letter N on the switch. Move the switch lever till it stops against the drill bit.
- Install the switch on the column, tighten the screws, and remove the drill bit.
- Check that the engine will start only in Park and Neutral, and that the backup lights come on only in Reverse.
The switch is mounted in the transmission and has no direct adjustment. Proper operation is determined by correct shift linkage adjustment.To replace the switch:
- Raise and support the front end on jackstands.
- Place a drain pan under the switch.
- Unscrew the switch from the transmission.
- Replace the switch, using a new seal. Tighten the switch to 24 ft. lbs.
- Refill the transmission.