4L80-E Automatic Transmission

1. Connect Tech 1 scan tool or equivalent to vehicle ALDL connector.

2. Start engine and ensure transmission is at normal operating temperature and fluid level is full.

3. Check for any transmission trouble codes and repair as necessary.

4. Depress brake pedal and move gear selector from park to reverse, reverse to neutral and neutral to D4. Gear selections should be immediate and not harsh.

5. Road test vehicle using shift speed charts.

6. If no trouble codes have been set and problem still exists, refer to "Troubleshooting."