GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2003 🢒 Kodiak C-Series (Crew) C4/C5 🢒 Driveline/Axle 🢒 Rear Axle Controls 🢒 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 Draining Reservoirs .

    4. Important: 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 in Air Brakes.
  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 in Air Brakes.

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

    2. Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

  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 in Air Brakes.
  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.