Neutral Safety Switch

Replace the neutral safety switch on a 1970 AMC Rebel Machine with 390ci V8 and automatic transmission to restore starting safety function and backup light operation.

Warnings

Tools required

Parts

• Neutral safety switch × 1 — Use OEM specification for Borg-Warner automatic transmission
• Transmission pan gasket (if fluid level drops significantly) × 1 — Use OEM specification

Fluids

• Automatic transmission fluid (DEXRON II or equivalent) — 1 qt

Preparation

1. Park vehicle on level ground and set parking brake firmly
2. Place wheel chocks behind rear wheels
3. Disconnect negative battery cable to prevent accidental starter engagement
4. Raise front of vehicle with floor jack and support on jack stands at frame rails
5. Allow transmission to cool if vehicle was recently driven

Procedure

1. 1

   Locate neutral safety switch
   From underneath the vehicle, locate the neutral safety switch on the driver's side of the transmission case, near the shift linkage. The switch has two or three wire connectors attached to it and is threaded directly into the transmission housing.
2. 2

   Disconnect electrical connectors
   Disconnect the electrical connectors from the neutral safety switch. There may be two separate connectors or one multi-pin connector depending on configuration. Note the position and routing of wires for reinstallation.
3. 3

   Position drain pan
   Place a small drain pan directly below the neutral safety switch. Expect approximately 1-2 cups of transmission fluid to drain when the switch is removed.
4. 4

   Remove old neutral safety switch
   Using the appropriate socket or wrench (typically 1-1/16" or 1-1/8"), unscrew the neutral safety switch counterclockwise from the transmission case. Work quickly once the switch begins to loosen to minimize fluid loss. Remove the switch completely and allow fluid to drain into the pan.
5. 5

   Clean switch mounting area
   Use a wire brush and shop rag to clean the threads in the transmission case where the switch mounts. Remove any old sealant, debris, or metal shavings. Ensure the mounting surface is clean and dry.
6. 6

   Install new neutral safety switch
   Thread the new neutral safety switch into the transmission case by hand to avoid cross-threading. Hand-tighten the switch until it seats against the transmission case, then snug with a wrench. Tighten firmly but do not over-torque as the switch body is typically brass or aluminum and can strip easily. The switch should be snug enough to prevent fluid leakage.
7. 7

   Reconnect electrical connectors
   Reconnect the electrical connectors to the neutral safety switch terminals in their original positions. Ensure connections are clean and tight.
8. 8

   Check and add transmission fluid
   Lower vehicle from jack stands. With engine off, check transmission fluid level on dipstick. Add fluid as necessary to bring level to the full mark. Use DEXRON II or equivalent automatic transmission fluid.
9. 9

   Reconnect battery and test operation
   Reconnect the negative battery cable. With parking brake set and foot on brake pedal, attempt to start the engine in Park position. Engine should start normally. Shift to Neutral and verify engine starts. Shift to Drive or Reverse and confirm engine will NOT start (this is the safety function). Check that backup lights illuminate when shifted into Reverse.

Reassembly

1. No disassembly was required beyond switch removal
2. Ensure all electrical connections are secure and properly routed away from exhaust components

Verification

• Engine starts in Park and Neutral positions only
• Engine does not crank when shifter is in Drive, Reverse, or Low positions
• Backup lights illuminate when transmission is shifted into Reverse
• No transmission fluid leaks visible around neutral safety switch after test drive
• Transmission fluid level is at proper full mark on dipstick

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