GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1999 🢒 GMC C-Series Medium Duty Truck B7 🢒 Transmission/Transaxle 🢒 Automatic Transmission - Allison 🢒 Vacuum Modulator Inspection

    Object Number: 201539 Size: SH
  1. Inspect the vacuum modulator hose and the vacuum hose for transmission oil.
    2. • If oil is present, replace the modulator. Refer to Transmission Modulator Replacement .
    • Gas or water vapor in the vacuum hose and the modulator is expected and does not interfere with the normal operation of the modulator.
  2. Inspect the vacuum modulator hose and vacuum hose connections for vacuum leaks using the following procedure:
    3. 2.1. Apply a solution of soap and water to the modulator hose and vacuum hose connections.
    2.2. With the engine running, check for air bubbles on the following parts:
       • The modulator hose
       • The vacuum hose
       • The vacuum hose connections
    2.3. If air bubbles are present, replace the section of vacuum hose that is leaking.