Operational Test
- Block the wheels.
 
- Apply the parking brake.
 
- Start the engine. Charge the air system to the air compressor  governor
cutout point.
 
- Stop the engine.
 
- 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. | 
 
- Remove the wheel blocks.
 
Air Leakage Test
- Block the wheels.
 
- Apply the parking brake.
 
- Start the engine. Charge the air system to the air compressor  governor
cutout point.
 
- Stop the engine.
 
- Shift the two-speed rear axle shift control valve lever to HIGH.
 
- 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.
 
- If the air leakage is too much, repair or replace the two-speed  rear
axle shift quick release valve.
 
- 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.
 
- Remove the wheel blocks.