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Home >> Buick >> 2007 >> Lucerne CX >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 9 (Automatic Transaxle - 4T80-E - Service, Diagnosis & Troubleshooting) >> Road Test >> Manual Downshifts

Manual Downshifts

WARNING: This page is about a different variant/trim than selected.

The shift solenoid valves do not control manual downshifts. Manual downshifts are hydraulic. The solenoid states will change during, or shortly after a manual downshift is selected.

Manual 4-3 Downshift

  1. Place the gear selector in the OVERDRIVE position.
  2. Accelerate the vehicle to 64-88 km/h (40-55 mph) in FOURTH gear.
  3. Release the throttle while moving the gear selector to THIRD.
  4. Verify the following:
    • The TCC releases
    • The transmission downshifts immediately to THIRD gear
    • The engine slows the vehicle

Manual 4-2 Downshift

  1. Place the gear selector in the OVERDRIVE position.
  2. Accelerate the vehicle to 64-72 km/h (40-45 mph).
  3. Release the throttle while moving the gear selector to SECOND.
  4. Verify the following:
    • The TCC releases
    • The transmission downshifts immediately to SECOND gear
    • The engine slows the vehicle

Manual 4-1 Downshift

  1. Place the gear selector in the OVERDRIVE position.
  2. Accelerate the vehicle to 64 km/h (40 mph).
  3. Release the throttle while moving the gear selector to FIRST.
  4. Verify the following:
    • The TCC releases
    • The transmission immediately downshifts to SECOND Gear.
    • The engine slows the vehicle.
    • The transmission downshifts to FIRST gear at the calibrated speed, typically 48-64 km/h (30-40 mph).
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