- Block the right front and rear wheels.
 
- Turn the Ignition ON - Do not start the engine.
 
- Place the transmission in NEUTRAL.
 
- Shift the transfer case into 4 LOW.
 
- Engage the differential lock switch.
 
- Raise the left front wheel off the ground. Refer to 
Lifting and Jacking the Vehicle .
 
Support the left front wheel with safety stands.
- Raise the left rear wheel off the ground. Refer to 
Lifting and Jacking the Vehicle.
 
Support the left rear wheel with safety stands.
- Attempt to rotate the left rear wheel 1 full revolution clockwise and counterclockwise by hand.
 
| •  | If the wheel does not rotate 1 full revolution in either direction, the locking differential is engaging properly. | 
 
| •  | If the wheel rotates more than 1 revolution in either direction, the locking differential is not engaging properly. | 
 
- Disengage the differential lock switch.
 
- Attempt to rotate the left rear wheel 1 full revolution clockwise and counterclockwise by hand.
 
| •  | If the wheel rotates 1 full revolution in either direction, the locking differential is disengaging properly. | 
 
| •  | If the wheel does not rotate more than 1 revolution in either direction, the locking differential is not disengaging properly. | 
 
- If the locking differential is not functioning properly, remove the differential and determine the cause of failure. Refer to 
Differential Replacement and 
Locking Differential Disassemble .