GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2009 🢒 TopKick C-Series (Conventional) C4/C5 🢒 Driveline/Axle 🢒 Rear Drive Axle 🢒 Differential Lock Relay Valve Replacement

Removal Procedure
  1. Apply the parking brake.
  2. Block the wheels.
  3. Drain all of the air reservoirs. Refer to Air Brake Reservoir Draining.

    4. Note: Tag the air lines for later installation.

  4. Remove the air lines at the differential lock relay valve. Refer to Hose and Line Replacement - Nylon Push-In Type Fitting.
  5. Remove the following components from the differential lock relay valve:
    6. • The nuts
    • The washers
    • The bolts
  6. Remove the differential lock relay valve from the right side frame side rail.
  7. Inspect the air lines for the following conditions:
    8. • Damage
    • Kinks
    • Wear
  8. Repair or replace the air lines as needed. Refer to Hose and Line Replacement - Nylon Push-In Type Fitting.

Installation Procedure
  1. Install the differential lock relay valve onto the right side frame side rail.

    2. Caution: Refer to Fastener Caution in the Preface section.

  2. Install the following components to the differential lock relay valve:
    3. • The bolts
    • The washers
    • The nuts

    Tighten
    Tighten the differential lock relay valve nuts to 12 N·m (106 lb in).

  3. Install the air lines at the differential lock relay valve (3). Refer to Hose and Line Replacement - Nylon Push-In Type Fitting.
  4. Start the engine. Charge the system to the air compressor governor cutout point.
  5. Stop the engine.
  6. Inspect for air leaks using a soap solution.
  7. Verify proper operation of the differential lock.
  8. Remove the wheel blocks.