For 1990-2009 cars

### Operational Test

1. Block the wheels.
2. Apply the parking brake.
3. Start the engine. Charge the air system to the air compressor governor cutout point.
4. Stop the engine.
5. Verify that the two-speed rear axle is operating properly.

5.1. | Verify that the two-speed rear axle promptly switches to the LOW range when the two-speed rear axle shift control valve lever is switched to LOW.

5.2. | If the two-speed rear axle shift motor is sluggish, switch the two-speed rear axle shift control valve lever to LOW. Verify that air vents through the exhaust port of the two-speed rear axle shift quick release valve.

5.3. | If air does not vent through the exhaust port of the two-speed rear axle shift quick release valve, repair or replace the two-speed rear axle shift quick release valve.

6. Remove the wheel blocks.

### Air Leakage Test

1. Block the wheels.
2. Apply the parking brake.
3. Start the engine. Charge the air system to the air compressor governor cutout point.
4. Stop the engine.
5. Shift the two-speed rear axle shift control valve lever to HIGH.
6. Inspect the two-speed rear axle shift quick release valve exhaust port for air leakage. Air leakage less than a 25.4 mm (1.0 in) bubble in 3 seconds is acceptable.
7. If the air leakage is too much, repair or replace the two-speed rear axle shift quick release valve.
8. Inspect the upper and lower valve body for air leakage. Air leakage is not allowed. If any bubbles appear, repair or replace the two-speed rear axle shift quick release valve.
9. Remove the wheel blocks.